Journal of the Society of Motion Picture Engineers

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JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX JULY, 1937 Number 1

CONTENTS

Page

Progress in the Motion Picture Industry — Report of the Prog-
ress Committee 3

Report of the Projection Practice Committee 39

Report of the Committee on Exchange Practice 50

Report of the Color Committee 54

Report of the Non-Theatrical Equipment Committee 57

Report of the Membership Committee 63

Toning Positive Film by Machine Methods . . J. M. NICKOLAUS 65

A Transmission-Measuring System Utilizing a Graphic Re-
cording Meter W. W. LINDSAY, JR. 68

Denham Studios of London Film Productsion, Ltd

L. C. FERMAUD 77

New Motion Picture Apparatus

The Super Simplex Pedestal J. FRANK, JR. 94

Current Literature 99

Obituary — Harry Pfannenstiehl 104

Spring, 1937, Convention at Hollywood, Calif.

Highlights of the Convention 106

Final Program 1 10

Society Announcements 116

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS. EDITOR

Board of Editors
J. I. CRABTREE. Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum; to members, $5.00 per annum
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y.
Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers in question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 250 W. 57th St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 463 West St., New York. N. Y.
Convention Vice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK. JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York. N. Y.

GOVERNORS

M. C. BATSBL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 250 W. 57th St., New York, N. Y.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE, 205 W. Wacker Drive, Chicago, 111.

PROGRESS IN THE MOTION PICTURE INDUSTRY*
REPORT OF THE PROGRESS COMMITTEE

Summary. — This report of the Progress Committee covers the year 1936. The
advances in the cinematographic art during that period are classified under the
headings: (7) Cinematography, (IT) Sound Recording, (III) Sound and Picture
Reproduction, (IV) Publications and New Books; (Appendix A) General field of
progress of the motion picture industry in Great Britain, (Appendix B) Motion
picture developments in Austria, (Appendix C) Report of the activities in the cine-
matographic field in Germany during 1936.

The Committee has been very successful in collecting material
illustrating new advances in cinematography during 1936. Since it is
practically impossible in a report of this nature to cover each and
every advance in the art, many deserving items will undoubtedly be
omitted. The greatest advances during the year seemed to take
place in the field of sound recording and reproduction, the most
interesting being the reproduction of push-pull recording and the
use of ultraviolet light in both recording and printing operations.
The year was noted by the introduction of a newer multicellular type
of horn system for theater use, so that considerably improved quality
of sound reproduction should be available to the public during 1937.

The Committee this year is including a special appendix dealing
with the motion picture industry in Germany, where considerable
activity both in sound recording equipment and in substandard
cinematography took place during the year.

The Committee wishes to acknowledge the courtesy of the follow-
ing firms for supplying materials and photographs for the report:
Bell & Howell Company; Electrical Research Products, Inc.; Gen-
eral Radio Company; International Projector Corp. ; Mole-Richard-
son, Inc. ; RCA Manufacturing Corporation; Klangfilm, G. m. b. H.

L. N. BUSCH
G. A. CHAMBERS
A. A. COOK
R. E. FARNHAM

J. G. FRAYNE, Chairman
H. C. HUMPHREYS
W. LEAHY
J. L. FORREST
G. E. MATTHEWS

V. E. MILLER
PAUL SCHROTT
G. H. WORRALL
I. D. WRATTEN

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.

4 PROGRESS OF MOTION PICTURE INDUSTRY tf. S. M. P. E.

SUBJECT CLASSIFICATION

(I) CINEMATOGRAPHY
(.4) Professional

(1) Films and emulsions

(2) Cameras and accessories

(3) Camera lenses

(4) Stage illumination

(5) Color

(B) Substandard

(1) Films

(2) Cameras

(3) Projectors

(4) Color

(5) Miscellaneous

(FT) SOUND RECORDING

(1) General

(2) Recording equipment

(3) Accessories

(III) SOUND AND PICTURE REPRODUCTION

(1) Sound equipment

(2) Projectors and accessories

(IV) PUBLICATIONS AND NEW BOOKS
APPENDIX A

General field of progress of the motion picture industry in
Great Britain.

APPENDIX B

Motion picture developments in Austria.
APPENDIX C

Report on the activities in the cinematographic field in Germany
during 1936.

(I) CINEMATOGRAPHY
(A) Professional (35 Mm.)

The fact that there have been no startling innovations in pro-
fessional motion picture photography need not detract from the fact
that the steady forward movement indicates a healthy condition and
a tendency to greater permanency in the art. The year 1936 saw no
new or upsetting inventions or processes, but a general improve-
ment in both materials and technic in the several phases of the allied
cinematographic arts.

(1) Films and Emulsions. — During the past year numerous im-
provements have been made in the Kodachrome process and, in
addition, a new type has been announced.1 The latter is intended

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 5

for use with artificial light, and is compensated for the difference in
color between incandescent lamps and daylight, for which latter
source the original Kodachrome film was balanced. Filters have
been provided for interchangeably using either film with either source.
At the present time either type of emulsion is available in each of
the amateur substandard widths, 8- and 16-mm., and, in addition,
the film is available for miniature still cameras in the 35-mm. width.

Announcement has been made by Agfa of a new color-film based
upon the Fischer process.2 Several emulsions coated upon the same
support contain components in the separate emulsions that react
with the developing solution to produce colored images. Following
the development of the colored images the metallic silver is removed
by a suitable bleach, thus increasing the transparency of the image.

In the field of black-and-white films for the substandard cameras,
a new high-speed panchromatic film has been made available.3

A new infrared-sensitive negative film for professional production
work has been made available to the trade.4 This type of material,
in conjunction with red filters, is used principally for special effects
such as night photography in full daylight. Since the film is insensi-
tive to yellow-green, only a light red or orange filter is necessary to
hold back the ultraviolet and blue for night effects. This not only
speeds up the possible exposure, but also produces a much better
balanced and more realistic picture.

A radically new type of film for the production of duplicates from
transparencies by a single step has been described in the JOURNAL.*
This film takes advantage of the solarization property of emulsions.
The reversal point in sensitivity is obtained not by overexposing the
emulsion to light but results rather from a ripening process during
manufacture in the presence of fog producing agents.

A method for dry-hypersensitizing unexposed films and for treat-
ing the latent image prior to development consists in exposing the
sensitive material to mercury vapor. This method, as outlined pre-
viously in the JOURNAL6 consists in exposing the material to mercury
vapor at room temperature and atmospheric pressure for a period of
30 hours, if the film is not wrapped, or for six to eight days if the film
is enclosed in the usual photographic black paper.

The effect of humidity upon the sensitivity of photographic emul-
sions has been studied by Charriou and Valette,7 who reached the
conclusion that exposure to excessive amounts of moisture reduced
the emulsion sensitivity. Neither alcohol nor acetone was as effec-

6 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

tive as water vapor in this respect. Rolleau reports a study of the
effect of temperature upon sensitivity.8 The results indicate that
the sensitivity of an ordinary emulsion decreases with temperature
in the range +20° to — 60°C. Orthochromatic and panchromatic
emulsions were found to have sensitivity maximums at approxi-
mately — 20°C., but this maximum disappeared when only blue light
was used for exposing these materials.

The development properties of peptized emulsions prepared with a
minimum of gelatin with agar agar used to facilitate coating were
studied by Steigmann.9 Experiments by Marinesco10 indicate that
the blackening of photographic emulsions by supersonics is similar to
that produced by light.

An experimental factory for the manufacture of photographic
materials was opened during the past year11 in the U. S. S. R. The
research workers in that country have reported a large number of
observations on photographic phenomena in a series of papers.12
The subjects dealt with include the aging of emulsions ; the relation
between the method of preparation of an emulsion and its resolv-
ing power; the adsorption of sensitizing dyes by silver halides ; and
other effects dealing with latent image phenomena.

A systematic study of a group of cyanine sensitizing dyes has been
reported by Hamer and Fisher,13 while the properties of halogen-
substituted cyanine dyes have been discussed in a separate paper.14
Additional progress in the preparation of new sensitizing dyes has
been reported in a series of papers by Brooker.16 A historical
review of sensitizing dyes and their applications to photography has
been given by Mees.16

(2) Cameras and Accessories. — Though an unblimped silent
camera failed to make an appearance, progress may be reported
in that field. A number of studios equipped themselves with NC
Mitchell cameras, to be used in conjunction with very light-weight
blimps. Two major studios gave the latest Debrie Super-Parvo
Cameras practical tests in actual production with favorable results.
But perhaps the most outstanding camera so far developed has been
made by the Twentieth Century-Fox studios, under the supervision
of Grover Laube, as previously reported by the Committee.17 It
has made eight feature productions, and plans are now under way for
the manufacture of several of them for use in the Fox studio. Aside
from its being satisfactorily silent unblimped, it provides a greater
shutter opening than is commonly used; has an improved optical

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 7

system which speeds up its use ; the finder is not only more brilliant,
but, due to its closeness to the shooting lens, parallax has been virtu-
ally eliminated. Its movement, with a 200-degree shutter opening,
and very fast acceleration and deceleration, permits the film to be
perfectly at rest during exposure, increasing greatly the definition
of the image. It is undoubtedly a big step forward in camera
design.

Columbia Studios developed a direct motor drive for high-speed
camera work, remotely controlled by a rheostat, providing a smooth
movement from 24 to 192 frames per second. This eliminates the
gear-box with its attendant unsteadiness. This studio also de-
veloped a variable diffusing device, or, rather, improved several
existing devices, wherein the diffusion may be varied as needed,
particularly in moving from a long shot to a close-up, where constant
diffusion is undesirable.

(3) Camera Lenses. — Hal Mohr has reported a useful method of
achieving greater depth of field in photography.18 It consists in
using a lens so mounted that it can be rotated about its nodal point,
and setting the lens angle for each shot so that the near and far
objects are in best focus on the film. The effect is exactly the same
as if the camera were equipped with a swing-back.

Several articles have appeared during the year that are of funda-
mental interest to designers of optical equipment. Klughardt and
Otto give measurements of the actual light transmission through
photographic lenses19 and show that the losses in modern high-
aperture lenses are very great. Pritschow has analyzed the influence
of optical and mechanical centering on high-speed anastigmats.20
An interesting article on the new organic glasses has also appeared.21

(4) Stage Illumination. — For the period March 1, 1936, to March
1, 1937, several new types of lamps have been made available.
Perhaps most important is the No. 2 Photoflood introduced by the
two Mazda Lamp companies as of July 1, 1936. This lamp has
double the light output of the familiar No. 1 size. Its rated life is
6 hours. Its greater light output makes it especially useful for
amateur cinematography, particularly for color photography.

The entire group of high-wattage studio lighting lamps such as
the 5000-watt G-64 bulb; 10,000-watt G-96 bulb, and 2000-watt
G-48 bulb have been made available at higher efficiency (temperature),
and all lamps are designed for the same temperature, namely, 3380°
K, for color motion picture photography. These lamps are desig-

s

PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

nated CP, as contrasted with the designation MP for the regular
motion picture types used for black-and-white photography. On
account of the importance that all sources produce light of the same
color for color work, the newer practice of designing for a fixed color
of light has been adopted for the CP types. The Movieflood lamp
made available several years ago is now a part of the CP group.

Another new lamp designed especially for motion picture photog-
raphy is the 1500-watt, 115-volt T-24 bulb, medium bipost type.
This lamp is of the CP type intended for use in color work, and was
developed especially for the new Mole-Richardson Inky scoop.
The lamp has two rather unusual features: it represents the first

FIG. 1.

Flood Flash lamp and control equipment.
(Courtesy General Electric Co.)

use of the new medium bipost base — smaller than the familiar Mogul
bipost base now used on the 2000- and 5000-watt studio lamps, and
it incorporates a wire mesh screen mounted above the filament,
which absorbs the blackening that usually collects upon the bulb
and greatly improves the maintenance of the initial light output of
the lamp throughout life. The lamp is intended to burn base up.

The past year has seen a considerable increase in the utiliza-
tion of arc lamps as sources of photographic illumination. To meet
this demand Mole-Richardson, Inc., have developed a new 65-ampere
high-intensity arc (M-R Type 65), designed to meet the demand for
a small, high-intensity arc spotlamp to match the characteristics
of the Type 90, 120-ampere, and Type 170, 150-ampere, H-I arc

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 9

spotlamps. This lamp has been designed so that its spectral char-
acteristic in photography closely matches that of the higher powered
units.

The same company announces that the Solarspot style of lamps,
which have proved so advantageous for motion picture photog-
raphy, have been augmented by the addition of the M-R Type 206,
500-watt, and the M-R Type 208, 1000-watt Solarspots. These
lamps follow the general design incorporated in the 2000-watt Junior
Solarspot and the 5000-watt Senior Solarspot,17 and have been de-
veloped to meet the demand for smaller lamps having a wide range
of utilization.

A new type of lamp of special interest to still picture photog-
raphers is the new Flood Flash lamp announced by the General
Electric Company, and shown in Fig. 1 with its control equipment.
This is a 100- watt mercury lamp, mounted within a protective outer
bulb. It can produce on the average of 30 lumens per watt, or as
much light as the standard 200-watt filament lamp. This lamp may
be flashed hundreds of times, the duration of the flashes being of the
order of l/zo sec., permitting it to "stop" ordinary motion.

(5) Color.— In the color field, no doubt Technicolor, with their
several pictures such as Ramona and Garden of Allah, showed the
most pronounced improvement in the rendering of natural color and
make-up. However, Cinecolor, Magnacolor, Cosmocolor, Dufay-
color, Dunning, Keller-Dorian, and others came to the fore with
strong claims. The quality of some of their work is such that it
is safe to predict that a very strong color influence will be felt during
the coming year. The projection of color backgrounds, and the
painting of such backgrounds and the consequent matching of them
photographically has been done very successfully, and will further
the cause of color work immensely.

The improvements in Kodachrome1 and the impending introduc-
tion of the new three-color process by Agfa2 lends active interest to
color photography and augurs well for the future of color in the
cinematographic field.

(B) Substandard Classification

Progress in American substandard cinematography during 1936
was confined mainly to improvement in existing equipment, film,
and methods. There has been no outstanding change in the equip-
ment designed. Manufacturers have concentrated their efforts to

10 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

simplify and refine, apparatus. Sixteen-mm. projectors have been
continually improved so that now the quality of both picture and
sound compares favorably with that of 35-mm. equipment. In the
meantime film manufacturers also have improved their products and
have kept abreast of the increased demand for finer-grained films,
made necessary by the increased size of screen images.

These improvements are opening new fields to 16-mm. film, which
is rapidly leaving the strictly amateur classification to enter the semi-
professional field ; not as a competitor to 35-mm. film, but rather to
augment it by filling the need of the smaller communities for film
education and entertainment where the expense of 35-mm. equip-
ment is prohibitive. Realizing this, one of the large film producers
has, for the first time, announced the release of certain 35-mm. feature
pictures on both 35- and 16-mm. film.

The popularity of 8-mm. film is slowly increasing, being promoted
by the development of well-built, satisfactory, low-priced cameras
and projectors. Here, as in the 16-mm. field, the 8-mm. size is
making amateur movies possible where the cost of the 16-mm. film
and equipment is too great.

Abroad, 1936 has witnessed the introduction of many new develop-
ments in equipment and processes. Because of the several standards
of width of film in popular use, European manufacturers of equip-
ment have found it necessary to adapt their projectors to accom-
modate various widths. In sound equipment flexibility was pro-
vided in the claw movement to make possible the projection of
sound-films produced according to the SMPE or the European
standard. With the adoption of a single international standard
(the SMPE) in 1936, it can be expected that this confusion will
soon disappear.

(1) Films. — Hypan, a high-speed, fully panchromatic, fine-grain,
non-halation, reversible film for outdoor use was produced by the
Agfa Ansco Corporation. Kodachrome Type A,1 for use with arti-
ficial light, was introduced by the Eastman Kodak Company.
Gevaert announced the introduction on the American market of an
Ortho, a Panchro Super and a Panchro fine-grain reversal film.
Processing stations were established in the United States for develop-
ing the film. Gevaert double-8 reversible. film has also been made
available on the American market.

In England, Ilford announced the introduction of Selo fine-grain
reversal film. The film has a tinted base, which, it is claimed,

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY

11

provides protection against halation and produces a more pleasing
screen image during projection. Ilford also entered the field with
a 9.5-mm., reversal, fine-grain film supplied in 30-ft. magazines.

In Germany, Agfa has announced a new color-film for 35-mm.
miniature and 16-mm. motion picture cameras.2

(2} Cameras. — During 1936, the Eastman Kodak Company
placed upon the market a magazine Cine-Kodak — a 16-mm. motion
picture camera which eliminates the difficulty of threading. The
loading is so simple that it can
be accomplished in three seconds.
The entire range of Cine lenses is
available to fit this camera, from
the standard 1-inch lens to the
6-inch telephoto. The camera
may be operated at half speed,
normal speed, or at 64 frames per
second. Another Cine - Kodak
was also announced during the
year, the Model E, in the low-
price range. In this camera, the
supply and take-up spools are in
the same plane, for simplifying
threading. The camera is sup-
plied with a fixed-focus, //3.5
lens.

The Keystone Manufacturing
Company introduced a new line
of cameras of the 8-mm. type
which will accommodate either
ordinary 8-mm. or double 8-mm.
film. The cameras are equipped with fixed-focus lenses and have
adjustable speed. The Universal Camera Company of New York
announced the Univex single 8-mm. camera, intended to be sold in
the low-price field. Paillard-Bolex announced to the American
market a new 16-mm. camera having many special features: speeds
8, 16, 24, 32, and 64 frames; backward rewind for trick work; auto-
matic threading; special view-finder to prevent parallax; audible
footage indicator; visual focusing; and automatic footage indicator.
The camera takes standard 100-ft. rolls of 16-mm. film. It has a
turret lens mount and its weight is about six pounds. Zeiss-Ikon

FIG. 2. Bell & Howell double-8
camera.

12

PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

abroad announced a new model 8-mm. camera known as Movikon 8.
The camera is readily adjusted to take either single- or double-8
film, the change-over being effected by the reversal of a single
sprocket, which may be accomplished in a few seconds. The
camera is equipped with a Zeiss //2 Sonnar lens. It has an optical
range-finder and many other special features. Bell & Howell have

FIG. 3.

Model EE Kodascope.
Eastman Kodak Co.)

(Courtesy

announced a new double 8-mm. camera using the Eastman type
of double 8-mm. film (Fig. 2).

(3) Projectors. — A new Kodascope, Model E, and, more recently,
a modification designated EE, was introduced. This Kodascope
combines most of the desirable features of the Model L, such as
interchangeable lamps up to 750 watts, and interchangeable lenses,

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 13

including the 2-inch //1. 6. The performance of this Kodascope is
thus on a par with that of the Model L, although its price is very
much lower. It is shown in Fig. 3.

Bell & Howell introduced a new 16-mm. sound projector known as
the Model 138, intended for home and school use. It may be
equipped with a 750- watt lamp and will accommodate 1600-ft. reels.
Keystone developed a new series of 16-mm. projectors of die-cast
construction. The projectors will accommodate a 750-watt lamp
and may be equipped with an //1. 6 projection lens. Special features
of the projectors are the forward or reverse projection and unusually
silent operation. The Universal Camera Company of New York
brought out an 8-mm. projector intended for the low-price field.
Andre Debrie, Inc., of New York announced a new 16-mm. sound
projector to meet the requirements of 16-mm. professional equipment.
The machine embodies the features of high-powered illumination,
extreme simplicity in threading, and a claw movement that is readily
adaptable to either the SMPE or the former European sound-track
standards. Ample cooling is provided so that the machine may run
continuously without danger of overheating. Paillard-Bolex abroad
announced a new projector accommodating 8-, 9.5-, and 16-mm.
films. This new projector is said to have an unusually efficient light-
source making large screen images possible with the smaller films.
British Industrial Films announced a new 16-mm. sound projector
built to take either the former European or the SMPE sound-track.
The machine is strongly built for heavy-duty service, and is claimed
to set a new standard of quality in type of sound reproduction.

(4) Color. — As has already been pointed out, a special Koda-
chrome emulsion designed for use with artificial light was introduced
during the year. This eliminated the use of a filter, and at the same
time increased the effective speed about four times when used with
artificial light. During the year, both the regular and the new Type
A Kodachrome were made available in the 8-mm. size. The speed
of regular Kodachrome was increased until it is now as fast as regular
Panchromatic film. Processing stations for Kodachrome have been
opened in London, Paris, and Australia, as well as in Chicago, Los
Angeles, and Rochester.

Although Pola-Screens have been available for some time, it was
not until the past year that they were made available for Cine-
Kodaks. Their use is highly desirable under certain conditions,
such as for avoiding reflections from plate-glass windows, floors, etc.

14

PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

With Kodachrome, they are particularly valuable for rendering deep
blue skies. This is the only way the blue color of the sky can be
accentuated when using a color-film.

(5) Miscellaneous. — Two new lenses of wide usefulness were
introduced for 16-mm. cine work: the 21/2-inch//2.7 and the 4-inch
f/2.7. A new optical view-finder for the Cine Special was introduced,
which corrects for parallax. The Ampro Corporation has designed
a special projector condenser lens of the duo convex type which is
said to increase the light output considerably. Bell & Howell brought
out a new automatic film splicer for single- and double-perforated

FIG. 4.

High-quality recording channel (Courtesy Electrical Research
Products, Inc.).

films, designed after models used successfully in the 35-mm. field.
New lenses of various apertures and focal lengths for the Filmo 8
and Double 8 were announced by the same company. The Pola-
Screen was introduced by the Eastman Kodak Company. The
RCA optical printer, announced late last year, has proved very'
popular. 1936 has witnessed a substantial increase in the number
in use and the amount of film recorded.

(H) SOUND RECORDING

(1) General. — Progress in both recording and reproducing sound
was very substantial during the year 1936. The use of class A

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY

15

push-pull recording mentioned in last year's report began to expand
considerably during the past year. Universal Studio made a
complete installation of push-pull recording and reproducing chan-
nels, while experimental channels were put into operation at Colum-
bia, General Service, and United Artists Studios. Squeeze-track
recording, pioneered by the M-G-M Studios, was used very ef-
fectively during the past year as a means of extending the volume
range in such outstanding productions as The Great Ziegfeld, and

FIG. 5. Portable recording machine. (Courtesy Elec-
trical Research Products, Inc.)

more recently in May time. Columbia also did some experimental
work in this field during the past year.

In reproducing, two-way horn systems, following the lead of the
Fletcher two-way horn development, came into wide-spread use
during 1936. Both Electrical Research Products, Inc., and RCA
Manufacturing Company have offered these systems to the trade,
while the Shearer horn system has had wide popularity.22 The basic
element of all these systems is the multicellular horn, credited origi-
nally to E. C. Wente of the Bell Telephone Laboratories, described
in last year's report.

16 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

In order further to improve sound reproduction in the theater, a
Committee of the Academy of Motion Picture Arts & Sciences has
been actively investigating the optimal theater characteristic for
sound systems. A report has been issued by the Committee and it
is thought that general adherence to the recommended characteristic
may prove generally beneficial to the industry.

(2) Recording Equipment. — During 1936 Electrical Research
Products, Inc., completed the development of a high-quality portable
recording channel (Fig. 4.). Two units forming parts of this channel,
namely, the pick-up unit and main amplifier, were completed during
1935 and reported by the Progress Committee last year. The com-
plete channel is now in use by the industry and consists of the follow-
ing principal components in addition to the two named above:

FIG. 6. Four-ribbon light- valve. (Courtesy Electrical Research
Products, Inc.)

A portable noise-reduction unit of the carrier modulation type; a
new recorder control unit, providing the usual recorder control
facilities; and, in addition, an oscillator, light-valve overload bridge,
and photocell amplifier output stage. The portable recording
machine (Fig. 5) used with this channel has been designed primarily
for quality recording, but has been made as light in weight as possible
without penalizing its performance. In use, the channel is set up
with the recording machine on top of the recorder control unit, with
the noise-reduction unit at the side. This places all the operating
controls within easy reach of the operator, and since the oscillator
delivers sufficient power to modulate the light-valve 100 per cent,
it is possible for the operator to set up and test the equipment during
rehearsal without interfering with the mixer's monitoring circuit.

During 1936 Electrical Research Products, Inc., developed and
placed at the disposal of the industry experimental equipment for

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY

17

recording and reproducing push-pull sound records. A four-ribbon
light-valve (Fig. 6) is used for recording all push-pull sound-tracks.
This light-valve is of the clamped-bridge biplane type, and has proved
quite rugged, holding its tuning and spacing for a long period of
time. It can be used to produce either the push-pull or conventional
type of sound recording.

RCA announces that in the past year several of the major studios
of Hollywood have been added to the list of licensees of the RCA
Manufacturing Company. Commercial equipment for push-pull

FIG. 7. RCA portable truck channel.

recording with ultraviolet light was manufactured for installations
at Hollywood, New York, and London. Many new custom-built
trucks have also been provided with the new push-pull ultraviolet
light recording equipment (Fig. 7).

Demonstrations showing push-pull ultraviolet recordings printed
with ultraviolet light on the RCA non-slip printer were made in
Hollywood, New York, and London, and created a great deal of
interest. It is claimed that the use of ultraviolet light23 in making
push-pull and standard variable-width recordings has increased the
resolution of the sound-track, reduced fogging due to halation, and

18

PROGRESS OF MOTION PICTURE INDUSTRY [J. s. M. P. E.

decreased the chromatic aberration of the lens system. This im-
provement is very definite in listening tests, and quite pronounced
when the sound-track is viewed under the microscope. The RCA
non-slip printer24 with ultraviolet printing appears to show consider-
able improvement over existing printers. It is claimed that its
design eliminates slippage between the negative and the raw stock,
and provides automatic compensation for various values of film
shrinkage. The use of this printer is free
to RCA licensees, and several printer
manufacturing companies have obtained
licenses to manufacture and sell them. The
new unidirectional microphone28 (Fig. 8)
was introduced this year, and a small
number of units were made available to
several motion picture studios for experi-
mental use. Tests made so far indicate
that this microphone has characteristics
particularly useful for film recording.

(5) Accessories. — Electrical Research
Products, Inc., has announced a peak read-
ing volume indicator, which, as its name in-
dicates, provides a ready means for visually
determining the peak value of sound cur-
rent. The indication of peak values of
voltage is practically independent of wave-
form, and the meter may be adjusted to
have a slow restoring action for easy read-
ing. The instrument provides a full indi-
cation for sounds of very short duration.

RCA has introduced a new neon volume
indicator that makes it possible to monitor the volume level of
the sound-track visually over a volume range of 48 decibels. It
provides an accurate indication of peak voltage over the entire
volume range; and control changing is eliminated. The unit is
unique in operation, size, and design.

The General Radio Co. has introduced the 759-A sound-level
meter (Fig. 9), which, although developed primarily for making
industrial noise measurements, has extensive application in various
sound reproduction fields, particularly in measuring studio back-
ground noise and the noise level in the projected sound record.

FIG. 8 . Unidirec-
tional microphone.
(Courtesy RCA Manu-
facturing Co.)

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 19

The General Electric Company announce that the 10-volt, 71/%-
ampere, T-8 bulb lamp has been developed to a point where it does
a fair job of recording by ultraviolet light. This has been done by
the use of a bulb of ultraviolet-transmitting glass, and by using the
horizontal filament coil. The advantage of winding the coil in an
arc of about 5/g to 3/4-inch radius is twofold : closing up the turns on
the concave side increases the quantity of the higher-temperature
radiation emitted from the interior of the coil, and opening up the

FIG. 9. Sound-level meter. (Courtesy General Radio Co.)

turns on the convex side gives this higher-temperature radiation a
better opportunity to escape from the interior of the coil, and also
improves the uniformity of distribution of the radiation.

(Ill) SOUND AND PICTURE REPRODUCTION

Little notice has come to the Committee of new picture head pro-
jectors in this country, although several new or improved sound
attachments were introduced during the year.

(1} Sound Equipment. — Electrical Research Products, Inc., has
brought out the Western Electric high-quality heavy-duty reproducer
set coded T A -7400, forming part of the Mirrophonic sound system

20

PROGRESS OF MOTION PICTURE INDUSTRY [J. s. M. P. E.

(Fig. 10). It has a sealed precision kinetic scanner to insure uni-
form speed of film propulsion, and utilizes the latest type of projection
optical scanning capable of accommodating single, push-pull, or
double sound-track. In addition to these immediately applicable
facilities, it has been designed with the thought in mind of its adapt-
ability to probable future developments in sound recording.

In the Western Electric diphonic speaker system (Fig. 11), Elec-

FIG. 10. Western Electric high-quality reproducer.

trical Research Products, Inc., has made available a speaker combina-
tion that assures a quality of reproduction more natural and less
machine-like than any previously attainable. The cellular con-
struction of the high-frequency horn distributes the sound uniformly
to all parts of the theater. The ample load-carrying capacity pro-
vides a greatly increased dynamic range with the same natural
quality throughout.

RCA Manufacturing Company has introduced the type 1060 high-
fidelity sound attachment (Fig. 12), which has a number of new
features over previous designs. This unit may be used to reproduce

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 21

FIG. 11. Western Electric diphonic loud speaker system.

22 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

either push-pull or standard recordings. A unique and compact
design of push-pull optics is employed, containing a prism assembly
for bisecting the light-beam, so designed that all parts are readily
accessible for cleaning and observation. A three-point rubber-
suspended center-plate includes all the sound reproducing parts (i. e.,
rotary stabilizer and sound drum, pressure and lateral guide rollers,
all optical parts, phototube and phototube transformer), which
effectively isolates these critical parts from vibration. On the main
casting are mounted all gears, driving sprockets, and the motor
drive assembly. The motor is itself rubber mounted, and employs a
universal coupling to the sound reproducer head. Another new
feature is the inclusion of a flywheel on the motor shaft, which further

FIG. 12. RCA type 1060 sound head (push-pull).

insures uniformity of speed and allows the standard three-second start-
ing time without reducing the starting torque, a particularly desirable
feature in cold booths. The rotary stabilizer and sound drum shaft
use newly designed ball-bearings with a grease seal to eliminate
difficult oiling and keep out dirt.

Further improvements have been made in the high-fidelity two-
way loud speaker system employed by the RCA Manufacturing
Company, to provide high efficiency, low distortion, and improved
directional and distribution characteristics. Multicellular horns
have been developed to provide a progressive series of sound-distri-
bution angles to accommodate any type of. theater.

The type PG-105 theater sound reproducing equipment has been
marketed by the RCA Manufacturing Company for theaters up to a
seating capacity of five hundred. This equipment employs the

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 23

high-fidelity rotary stabilizer sound attachment, and a two-way
high-frequency and low-frequency loud speaker system. Particu-
larly interesting is the new amplifier (Fig. 13), designed with special
consideration for accessibility and high-fidelity performance. The
inclusion of the monitor loud speaker in the amplifier cabinet simpli-
fies construction and increases accessibility.

(2) Projectors and Accessories. — The International Projector
Corporation has announced the new Super Simplex pedestal. This

FIG. 13. RCA type 1223 amplifier with
monitor loud speaker, for small theater
installations.

pedestal appears to meet all the requirements of modern projection
and sound reproducing equipment, permitting a steadiness heretofore
unequalled (Fig. 14). The same company has also introduced a
slip-in gate for the Super Simplex projector that can be easily and
quickly removed by unscrewing two thumb-screws. This permits
the projectionist to clean it carefully at will. It also assures positive
location of the guiding elements and is recognized as a device that
meets a requirement of long standing.

During the latter part of the year an intermittent sprocket that
was hardened and accurately ground was introduced for use with the

24

PROGRESS OF MOTION PICTURE INDUSTRY [j. s. P. M. E.

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 25

Simplex projector mechanism. The accuracy of the sprocket mate-
rially assists in projecting a satisfactory picture, and the hardening
process lengthens the life of the sprocket considerably. This sprocket
is now being furnished on all new and repaired Super Simplex mecha-
nisms and is unquestionably of the highest quality and accuracy of
any sprocket in use.

ERPI has introduced a new type of double-film attachment (Fig.
15), designed as an adjunct to the new Western Electric heavy-duty
reproducer. It provides a means of reproducing separate sound
and picture records on 1000-ft. reels and permits the use of 2000-ft.
reels when single film is run. The film in the double-film attachment
is guided by means of idler rollers, or a driven sprocket as an alter-
nate arrangement, and the film path is such that the sound-film enters
the sound-head in essentially the same manner as it does for normal
threading. There is no difference in the quality of sound obtained
from film operating from the double-film attachment compared to
that of film threaded in the standard manner. Strippers and idler
rollers have been so located that film "jams" are virtually impossible.

(IV) PUBLICATIONS AND NEW BOOKS

A number of valuable reports have been published during the past
few years by the Academy of Motion Picture Arts and Sciences,
Hollywood, Calif., and the British Kinematograph Society, London.
The reports of the Deutsche Kinotechnische Gesellschaft appear in
their official publication, Die Kinotechnik, and those of the Societe*
Francaise de Photographie et de Cinematographic in the Bulletin of
this society. In the U. S. S. R. the articles concerning motion picture
progress appear in two journals, the Soviet Kino Photo Industry, and
Photo Chemical Industry.

A new motion picture publication made its initial appearance in
January, 1936, known as the Journal of the Association of Cine-
Technicians (London).

Since the last report of the Committee in May, 1936, the books of
noteworthy interest that have appeared are as follows:

(1) International Motion Picture Almanac (1936-37); Quigley
Publishing Co., New York, N. Y.

(2) Year Book of Motion Pictures (1937), 18th Edition; Film
Daily, New York, N. Y.

(5) Kinematograph Year Book (1937); Kinematograph Pub-
lications, Ltd., London.

26 PROGRESS OF MOTION PICTURE INDUSTRY LJ. S. M. P. E.

(4) Jahrbuch des Kino-Amateurs (Yearbook of the Cine-Ama-
teur) (1937), edited by W. Frerk, Photokino Verlag., Berlin.

(5) Abridged Scientific Publications from the Kodak Research
Laboratories, Vol. 16, Eastman Kodak Co., Rochester, N. Y.

(6) American Cinematographers Handbook and Reference Guide ;
J. J. Rose, American Cinematographer, Hollywood, Calif.

(7) Kino-Photo Scientific Research Institute, Vols. 1-3 (In
Russian); Kinephotoisdat, Moscow.

(8) International Dictionary of Cinematography (English, Ger-
man, Italian, French); International Edition; E. Cauda, Editor.
Stab, Tip "Leonardo da Vinci" Citta di Castello.

(9) IX Congre"s International de Photographic Scientifique &
Appliquee (Ninth International Congress of Scientific and Applied
Photography), edited by L. P. Clerc; Revue d'Optique, Paris.

(10} Motion Picture Laboratory Practice; Eastman Kodak Co.,
Rochester, N. Y.

(11) Color Cinematography; A. Klein, American Photographic
Publishing Co., Boston, Mass.

(12) Natural Color Processes; C. E. Dunn, American Photographic
Publishing Co., Boston, Mass.

(13) II Cinematografo al Servizio della Scienza (Cinematography
in the Service of Science) ; Quadrante, Rome.

(14) Trick Effects with the Cine Camera; H. A. V. Bulleid, Link
House Publications, Ltd., London.

(15) Cine Titling Simplified; H. B. Abbott, Link House Publica-
tions, Ltd., London.

(16) Photography; C. E. K. Mees, G. Bell & Sons, London; also
MacMillan Co., New York.

(17) Photography To-Day; D. A. Spencer, Oxford University
Press, London.

(18) Filmentwurf, Filmregje, Filmschmitt (Amateur Films, Plan-
ning, Directing and Cutting); A. Strasser, 2nd Edit., W. Knapp,
Halle.

(19) Filmtricke und Trickfilme (Filmtricks and Trickfilms);
A. Stuler, W. Knapp, Halle.

(20) Exposing Cine Films; D. C. Smethurst, Link House Publica-
tions, Ltd., London.

(21) Filmen mit Kodak 8 (Filming with the Kodak 8) ; A. Stuler,
W. Knapp, Halle.

July, 1937] PROGRESS OF MOTION PICTUR'E INDUSTRY 27

APPENDIX A

GENERAL FIELD OF PROGRESS OF THE MOTION PICTURE INDUSTRY
IN GREAT BRITAIN

Since 1927, when the Cinematograph Films Act was passed,
British motion picture production has shown tremendously acceler-
ated growth. The increase in production has naturally been accom-
panied by improved facilities for making pictures, and enormous
sums of money have been spent in building new studios, making
additions to existing studios, and equipping them with the necessary
technical equipment. The year 1936 was an eventful one in the
annals of British production and it is hoped that a brief description
of certain of the new studios, laboratories, and additions to existing
studios, built during that year will be of interest to the reader.

New Studios. — May, 1936, saw the official opening of the London
Film Studios at Denham, Bucks., a completely self-contained pro-
ductipn center. There are seven separate stages, the four largest
stages being air-conditioned. These buildings are of reinforced
concrete construction, and the inside walls are covered with rock-
wool for sound absorption. The sound system used is Western
Electric. Complete protection from the weather is afforded by cor-
ridors which connect the stages with the administrative block and
the dressing room block. In the administration block are located
two theaters, one of which is large enough to seat comfortably three
hundred persons. The studio has one of the largest power plants in
the country, having an output of 4400 kilowatts.

Pinewood Studios at Iver Heath, Buckinghamshire, was officially
opened on September 30, 1936. The studios are designed on the
unit principle, each consisting of eight stages. It is understood that
two units will be built, making a total of sixteen stages, but on the
opening date only five stages of the first unit had been completed.
Constructed on a steel framework, with solid concrete walls eleven
inches thick, these stages show careful consideration necessary to the
various requirements of production. Internally, the walls and ceil-
ings are sound-proofed with slagwool. All approaches to the stages
are under cover, an obvious necessity when one considers the inclem-
ent weather prevalent in this country, and covered ways are also
provided between the workshops and stages. Further, a covered
space of about 15,000 sq. ft. in area is located in the center of the
unit. For sound recording the Western Electric variable-density
system is used.

28 PROGRESS OF MOTION PICTURE INDUSTRY [J. s. M. P. E.

Additions to Existing Studios. — During 1936 several English studios
engaged in extensive additions to their premises. With the additions
completed during the year Sound City Studios, Shepperton, Middle-
sex, now has seven sound stages, totalling 80,000 sq. ft. of floor space.
Built on the unit system, each stage has its own dressing rooms,
production offices, property rooms, and many of the necessary acces-
sory departments. In a separate block are contained twenty cutting
rooms and three theaters. Standard sound equipment for these
studios are the RCA ultraviolet and the Visatone sound systems.
The Warner Bros.-First National Studios at Teddington, Middlesex,
made extensive additions and alterations during the past year.
The old studio, which has been in use for five years, has been modern-
ized, and an entirely new sound stage has been built.

Studios in Course of Erection. — At the end of 1936 there were about
twenty-five studios, totalling in all more than seventy stages, avail-
able for production in this country, all situated in or near the London
area. Some of these studios possess excellent technical facilities,
and although others are not so completely equipped, it would cer-
tainly seem that the number of studios is more than ample for the
present requirements of British production.

New Laboratories. — Under construction during 1936, the new
Technicolor Laboratories at Harmondsworth will fill the require-
ments of those British producers wishing to make films in Technicolor,
and will also, presumably, print color releases from American nega-
tives. The buildings are brick faced, with long windows stretching
the whole length of the frontage on both floors. Of special impor-
tance to the Technicolor process, every room in which film is handled
is completely air-conditioned, special care having been given to the
control of temperature and humidity. Having a potential output
of about 36,000,000 feet per year of finished prints, the new Techni-
color Laboratory will take an increasingly active part in British
productions. Also under construction during 1936 were the Denham
Laboratories, situated close to the London Film Studios. The
building is completely air-conditioned, and for that reason double
glazed casement windows are used throughout. The windows in
the cutting rooms are glazed with Thermolux, which effectively
prevents light or heat rays from focusing upon material exposed in
the room. Including these two new laboratories there are now
twenty-one motion picture film processing laboratories in this coun-
try, all situated in or near London.

July. 1937] PROGRESS OF MOTION PICTURE INDUSTRY

29

Technical Advances. — The Western Electric Company has de-
veloped a portable 16-mm. sound-film reproducing system primarily
for road show service, and embodying a number of novel features
(Fig. 16). The projector employs a single 450-watt lamp, which is
used for the dual purpose of picture projection and sound scanning.
The main drive is a synchronous motor, and a series motor having a
saturated field constitutes the take-up mechanism. To compensate

FIG. 16. Western Electric, Ltd. (London), IG-mm. sound-
film projector.

for the high-frequency loss inherent in 16-mm. film, variable high-
frequency equalization is provided. Similarly an adjustable high-
pass filter is provided to reduce the base effect in reverberant halls.
Messrs. A. Vinten, Ltd., have a light gyroscopic tripod for light type
35-mm. professional cameras and for serious work in 16-mm. The
head is so constructed as totally to enclose the whole mechanism, and
the oiling is such that it does not need renewing for at least five
years. The head can be immediately removed from the bowl type

30

PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

spider and placed in a similar one of metal construction which can
be readily fixed to an aeroplane wing or a carriage window. Another

product for the year is an
optical printer for producing
double-8 amateur films from
16-mm. (Fig. 17).

Exhibition. — The year has in
all been an improved one for the
exhibitor, although there is some
concern over increased competi-
tion due to the number of new
cinemas. The consensus is
that the extensive building pro-
gram will ultimately be to the
benefit of the exhibiting side,
because obsolete redundant
cinemas will be eliminated.

The mutually advantageous
association between the motion
picture industry and broadcast-
ing has continued. Commenc-
ing in November, regular tele-
vision programs have been
radiated by the British Broad-
casting Corporation, and the
British Movietonews and Gau-
mont British News are televised
daily. At present, television is for home entertainment only in
London and environs, and is not yet a source of competition to the
exhibitor.

APPENDIX B

MOTION PICTURE DEVELOPMENTS IN AUSTRIA
PAUL SCHROTT*

The Austrian film industry operates under great handicaps. The
fact that there are only six million German-speaking inhabitants in
Austria reduces the profits of the film industry, especially when the
sales are limited to Austria. The sales field in Germany is of no

FIG. 17. Sixteen-mm. to double-8
reduction printer. (Courtesy W.
Vinten, Ltd., London)

* Technische Hochschule, Institut fur Technische und wissenschaftliche Kine-
matographie, Vienna.

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 31

great advantage, since only a very limited film import to that country
is permitted in return for export of an equal amount of photographic
material into Austria. Furthermore, Germany does not permit
payment of the imported goods in currency. Although the Austrian
film industry is technically and artistically well equipped to produce
large quantities of film, it can not avail itself of this opportunity
because of barriers set up by other countries.

The development of the photographic apparatus industry is cur-
tailed for the same reasons, although excellent facilities, installa-
tions, and ideas are available.

In recent years several pieces of photographic equipment have
been developed. The Ludwig Hauner Co. of Vienna produces
a camera whose outstanding feature is a trick-shutter. The adjust-
able sector of this device must be entirely open at the beginning of
the change-over, otherwise the sector will not be closed in the as-
signed number of turns of the crank. A shutter in which the change-
over can be started from different opening angles of the sector is
constructed by Ludwig Castagna Co.

Motion picture projectors are built by Friedl and Chaloupka,
Vienna. The framing is of special interest and is accomplished by
turning the Maltese cross about its axis. This form of construction
is unique and rather difficult, since the moving period must be kept
in constant step with the position of the revolving shutter. The
shutter is controlled directly by the driving mechanism, not depend-
ing upon the Maltese cross, while the Maltese cross is adjusted by
means of a differential gear to keep the moving period constant.
The shutter, of the metal barrel type, is arranged between light-
source and film. The safety shutter consists of a centrifugal
shutter within a barrel shutter. The double-hinged gate is of
interest. The gate hinge is close to the film- track in most pro-
jectors, so that loading the film and cleaning the film-track are diffi-
cult. The film is completely exposed upon opening the double-
hinged gate, and the difficulties mentioned are entirely eliminated.

The motor is mounted laterally and parallel to the base. An inter-
mittent mechanism between motor and projector permits frequencies
of 24, 25 l/t, and 27 frames per second.

The cylindrical lamp housing is lined with highly polished alumi-
num to prevent heat radiation.

Substandard film cameras and projectors are manufactured by

32

PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

Indicator

alvanometer

Objective

Cell iris
Grid screen

Parallel resistance

FIG. 18. Automatic camera
adjustment.

aperture

two firms. The automatic adjustment of the lens aperture of
a camera made by Eumig is of special interest. A selenium cell

with an adjustable shutter
coupled to the diaphragm is
placed next to the lens. The
operation of the mechanism is
illustrated in Fig. 18. At a
certain aperture of the lens or
of the photoelectric cell corre-
sponding to a certain exterior
brightness, the galvanometer
indicator points to zero, as can
be seen in the finder. If the
exterior brightness changes, the
indicator must be readjusted to
zero by turning the cell dia-
phragm. This changes the lens
aperture correspondingly. The
zero mark can be adjusted ac-
cording to the sensitivity of the emulsion used. If the camera is
not to be used for the standard number of exposures, namely, 16,
the corresponding change of the lens diaphragm occurs auto-
matically with the setting to the new speed.

A color-film process upon which the inventors Gschopf and Pokorny
have worked for years, nears completion and will be described in
the near future. It is the "Irix" process, which is similar to the
Technicolor process, but appears to have certain advantages over the
latter:

Pure dyes in a colloidal solution are used for dyeing the printing
matrix, instead of the usual hydrochlorides, acetates, sulfates, and
other salts. The inventors recognized that the gelatin of the ma-
trix as an amphoteric colloid absorbs the pure dye base very rapidly
as a unilaterally electrically oriented substance and sufficiently retains
it without chemical union, yet transfers it very rapidly and com-
pletely to the image carrier containing precipitants for basic dyes,
while even the slightest acid action causes rapid and complete bleed-
ing of the dye base from the matrix.

The absorption of these pure dye bases by the gelatin of the matrix
and the transfer from the latter to the image carrier takes place
within a few seconds. After the printing is completed, the matrix

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 33

does not retain the slightest trace of the dye, and cleaning is un-
necessary. The three color-separations are superimposed and the
resulting image is grainless, sharp, light-proof, and water-proof,
and not affected by most acids. In this lies the superiority of this
process over other imbibition processes.

The very simple exposure represents another advance of the in-
ventors' tripack. Entirely new methods have been used in its
making and in the emulsion technic in connection with sensitizing
dyes and antihalation coloring. The result is a material of very
high sensitivity, exposure range, excellent color separation, and
extreme sharpness. It is sufficient to point out that the upper
two emulsions of the tripack are almost perfectly transparent. This
process is far superior to the process using several emulsions on ac-
count of its wide exposure range and the extensive color correction
possible.

APPENDIX c

REPORT ON ACTIVITIES IN THE CINEMATOGRAPHIC FIELD IN
GERMANY DURING 1936

The year 1936 showed notable progress in the cinematographic
field, indicating clearly that whereas the 35-mm. film is intended
exclusively for the theater, the 16-mm. substandard film is going to
take its place more and more as far as schools, associations, and other
official arrangements are concerned, and in which the audience is
smaller than in the theaters. Also the business in the amateur
field showed a great advance in Germany in that the 8-mm. sub-
standard film is actually replacing the 16-mm. size. Consequently,
during the year a considerable quantity of new apparatus came
upon the market, covering the whole cinematographic field, and
it would be difficult to give all details in this short report.

The leading firm in the 35-mm. field, Klangfilm, brought out a new
sound-film recording camera under the name of Eurocord, about
which Klangfilm themselves write as follows:

"It was the aim of the development to produce an apparatus that
would comply, not only with regard to sound quality but also with
regard to operating characteristics, with the highly advanced require-
ments and would take into account the experiences of the last eight
sound-film years. Due to extensive tests the double variable-width
method was chosen for sound-film recording because it is superior to
other recording methods by virtue of the length of the straight-line
portion of the characteristic curve, and allows simple control of

34 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

the treatment in the photochemical process. The reduction of noise
is achieved by shading off the white parts of the sound area by means
of an additional diaphragm

"The recording device consists of an oscillograph having a dynamic
driving mechanism, the noise of which is suppressed by oil, the change
in the noise suppression due to changes of temperature being auto-
matically compensated. The control of the sound volume is effected
by optical pick-up and by a new sound volume indicator. This
indicator consists of two instruments, namely, one indicator for the
mean value and another for the peak value, both being arranged in a
casing the size of a normal measuring instrument so that both can be
read at one glance. The indicator for the mean value shows the
mean volume of sound, while the indicator for the peak value also
reacts on short impulses.

"The apparatus is available in two types, one for connection directly
to the main for work in the studio and the other one as a battery
apparatus for outdoor exposures. Four so-called room microphones
are used, two directional and two undirectional. The mixing table
is movable so that it can also be brought to the scene. The sound
camera is suitable for inner cassettes. The exposure is controlled
photoelectrically . ' '

Since, however, not only good sound recording apparatus is
required, but because there is also great interest in recording sound
for other purposes in a more economical manner, Klangfilm has
brought upon the market an apparatus about which they report as
follows :

"The broadcasting companies and certain scientific institutes
have suggested the development of a sound recording apparatus that
would allow high-quality recording and as long a reproduction as
possible, so that subsequent corrections, cuts, and splices could be
made. The apparatus should be easily movable and resist vibrations.
Such equipment is especially needed for the analysis of non-recurring
sounds which can not be done on the spot with sufficient accuracy.
Recording on normal 35-mm. film is uneconomical, and for that reason
Klangfilm is placing upon the market, at the beginning of 1937, new
apparatus, so-called "Schmallfilmgerate," intended for unperf orated
sound-film 1/6 of the normal film width (5.83mm.). The recording
and projection are carried out at the speed of the standard film."

In the same field Arnold & Richter, G. m. b. H., announce a new
hand-camera for 35-mm. standard film containing double cassettes

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 35

for 60 meters of film, which can easily be exchanged because the
supply reel as well as the take-up reel are included in the cassette
so that all threading is eliminated. The camera has a revolving
head for three lenses (//2.3, focal length 28-75 mm.). The most
important novelty of this new ARRI-Camera is the mirror-reflex
arrangement, which allows a clear, upright, and parallax-free image
of the picture during the running of the film. The motor for
driving the camera is arranged vertically below the camera, and
acts at the same time as a handle and stabilizer.

The Standard 7 Aero Projector of Eugen Bauer G. m. b. H. was fur-
ther improved last year, and a special characteristic is the flanged
motor provided with a fan for supplying the film-gate and the film
with cool air. This air impinges upon the film from four nozzles
through channels in the ground plate of the film-track.

As a further safety device, the air valves are controlled by the
air blast. This safety device, called the Flammex, switches off the
light-beam as soon as the film or a splice breaks, in the gate. In
connection with this device a cut-off switch for the driving motor
can be furnished which will stop the motor immediately when trouble
occurs.

Due to the increased use of substandard film for all purposes for
which the smaller film is sufficient, during the last year a great number
of film treating and film printing equipments were developed. The
Union Tonfilm maschinenbau und Vertriebs-Gesellschaft in Berlin
have marketed an optical reduction printer (35-mm. to 16-mm.),
an optical printer for 16-mm. film, a contact printer for 16-mm.
film, and a reproducing and cutting table for 16-mm. sound-film.

Regarding the brightness of the pictures in the theaters, certain
progress was made during the past year that is especially interesting
in connection with the efforts made by Opticolor and Siemens &
Halske in introducing the lenticular film in the theaters. During
the Olympic Games the Siemens-Berthon color-film was shown for
the first time, and it was reported that the satisfactory brightness of
the projected pictures was due to the design of a new lamp.

In the processing field, Arnold & Richter constructed fully auto-
matic developing machines for 35-mm. film with different footage
capacities. They also constructed for 16-mm. film a fully automatic
machine in three different sizes, which can be used also for processing
8-mm. film.

In the field of substandard cameras, Siemens & Halske have intro-

36 PROGRESS OF MOTION PICTURE INDUSTRY [J. S. M. P. E.

duced the Siemens Kino Camera F, using lenses of various manu-
facturers. Zeiss-Ikon have improved their Movikon 16 to include
such features as an automatic range-finder, four speeds, polarization
screen, and motor instead of spring drive.

One of the outstanding developments of the year has been the intro-
duction of the Zeiss-Ikon Movikon 8 camera, which is an improved
construction of the former Movikon 16. This camera can be used
for double-8 film as well as for normal 8-mm. film. Some of its fea-
tures are a Sonnar lens of the speed 1 :2 and focal length of 1 cm. in
Fis-focusing-mount (depth of focus from 1 meter to infinity at greatest
diaphragm). The bayonet mount provides for using additional
lenses, e. g., 2.5- and 7.5-cm. focal lengths. Portrait-attachments and
yellow filters are available. The apparatus has three speeds: 8, 16,
and 64 frames per second. A single-picture device is also provided.
The spring motor of the pull-down allows a run of 33/4 meters of
film. A scale at the side wall and in the finder of the camera gives
information about the reserve of the spring motor expressed in terms
of the unexposed length of film. The picture area of the finder
corresponds to that of the 1-cm. lens; for the 2-cm. lens an insertion
mask is provided. Siemens & Halske placed upon the market the
Kino Camera C8 for cassettes, which can be used with the Kodak
daylight spools. This camera is provided with a Busch-Glaukar
Anastigmat 1:2.5, 1.3-cm., and can be used for Cine Kodak 8 film
(for black-and-white) or for Cine Kodak 8 Kodachrome on the
usual 7.5-m. spools inserted into Siemens cassettes. Four speeds
(8, 16, 24, and 64 frames per second) are provided.

The firm of Niezoldi & Kramer have supplied a low-priced camera
for Kodak 8-mm. film, and a new model B Cine Nizo 8E, having a
speed of 8-64 frames and interchangeable lenses, as well as a Cine
Nizo 8 ZD which takes 7.5- and 15-m. daylight spools of double
8-mm. film, and permits speeds of 8 to 100 frames per second.

In the field of substandard projectors Siemens & Halske have
constructed a "Two-Film Standard Projector" for 16- and 9.5-mm.
film. Only the masks for the gate and the sprockets need be ex-
changed; otherwise the construction is the same as that of the
Siemens standard projector for 16-mm. film. Features include the
Siemens beater pull-down mechanism, interchangeable projection
lenses (Meyer Kinon Superior/, 3.5-, 5-, or 6.5-cm.), interchangeable
two-blade or three-blade rotating shutter; an efficiency of 130 lumens
with the two-blade rotating shutter and a 5-cm. lens; single-frame

July, 1937] PROGRESS OF MOTION PICTURE INDUSTRY 37

device ; adjustable speed ; and it can be used on direct current or
alternating current lines of the usual voltage.

Eugen Bauer announce that their substandard sound film repro-
duction equipment is available with Bauer sound head and Bauer-
Lorenz amplifier. The reproducer is provided with a rotating sound
drum and flywheel similar to the Roxy equipment. A special micro-
lens with an optical slit is provided. The apparatus is available
for 16- and 17.5-mm. film.

The firm Union, G. m. b. H., placed upon the market during the
last year a new substandard film projector "Gigant," which reaches
an efficiency of more than 150 lumens with a 23-volt, 5.3-ampere
projection lamp. The very simple internal construction of the pro-
jector is of special interest.

Also the firm Lytax-Werke improved their well known substandard
sound-film projector which is also characterized by its very simple
construction but which nevertheless is very stable and very suitable
for operating for long periods.

REFERENCES

1 Amer. Cinemat. (May, 1936), p. 218; (June, 1936), p. 264; (Sept., 1936),
p. 396; (Nov., 1936), p. 483.

2 "The New Agfa Process of Colour Photography," Phot. Jour. (Dec., 1936),
p. 612.

3 Amer. Cinemat. (June, 1936), p. 264.

4 MEYER, H.: "Describing Agfa's Infrared Film," Amer. Cinemat. (May,
1936), p. 194.

8 EARTH, W.: "A Film Emulsion for Making Direct Duplicates in a Single
Step," J. Soc. Mot. Pict. Eng., XXVII (Oct., 1936), No. 4, p. 419.

6 DERSCH, F., AND DURR, H.: "New Method for the Dry Hypersensitization
of Photographic Emulsions," J. Soc. Mot. Pict. Eng., XXVIII (Feb., 1937), No. 2,
p. 178.

7 CHARRIOU, A., AND V ALETTE, S. : "Influence of Water on the Sensitivity of
Photographic Emulsions," Comp. Rend., 202, (April 29, 1935), No. 18, p. 1528.

8 Rolleau, M. : "Influence of Temperature on the Sensitivity of Photographic
Emulsions," Comp. Rend., 202 (March 9, 1936), No. 10, p. 835.

9 STEIGMANN, A. : Phot. Ind., 34 (Jan. 1, 1936), p. 10.

10 MARNINESCO, N.: "The Law of Blackening of Photographic Plates by
Supersonics," Comp. Rend., 202 (March 2, 1936), No. 9, p. 757.

11 MIKHAILOFF, V. I., AND KNAPPE, V. A.: "The Opening of the Experimental
Factory at Kazan," Photo-Chem. Ind. (1936), No. 1, p. 40.

11 Kino-Photo Res. Inst. (Moscow), 3 (1935), p. 14.

13 HAMER, F. M., AND FISHER, N. I.: Proc. Roy. Soc., 154A (May 1, 1936),
p. 703.

14 BEILENSON, B., AND HAMER, F. M. : /. Chem. Soc. (Aug., 1936), p. 1225.

38 PROGRESS OF MOTION PICTURE INDUSTRY

15 /. Amer. Chem. Soc., 57 (Dec., 1935), pp. 2480, 2488, 2492. Ibid., 58 (April,
1936), pp. 659, 662.

14 MEES, C. E. K.: "Sensitizing Dyes and Their Applications to Scientific
Photography," Proc. Roy. Inst. Great Britain (Jan. 31, 1936).

17 Report of the Progress Committee, /. Soc. Mot. Pict. Eng., XXVII (July,
1936), No. 1, p. 3.

18 Amer. Cinemat., 17 (Sept., 1936), p. 370.

19 Photographische Industrie, 34 (May 27, 1936), p. 608.

20 Photo. Korr, 71 (Dec., 1935), p. 158.

21 J. Soc. Chem. Ind., 55 (Apr. 24, 1936), p. 319.

22 Report of the Progress Committee, /. Soc. Mot. Pict. Eng., XXVII (July,
1936), No. 1, p. 45,

** DIMMICK, G. L. : "Improved Resolution in Sound Recording and Printing
by the Use of Ultraviolet Light," J. Soc. Mot. Pict. Eng., XXVII (Aug., 1936),
No. 2, p. 168.

24 BATSEL, C. N. : "A Non-Slip Sound Printer," J. Soc. Mot. Pict. Eng., XXIII
(Aug., 1934), No. 2, p. 100.

25 OLSON, H. F. : "A Unidirectional Microphone," J. Soc. Mot. Pict. Eng.,
XXVII (Sept., 1936), No. 3, p. 284.

REPORT OF THE PROJECTION PRACTICE COMMITTEE*

Summary. — Among the projects under consideration by the Committee during the
past six months are those of screen brightness; its desirable values and methods of
measuring it; the question of using a visual test-pattern for checking screen illumina-
tion; revisions of the projection room plans; questions of projector motors and
take-ups, and difficulties incident to the starting of projector motors; requirements
of sound screens; and a recently initiated survey of theaters throughout the United
States to determine not only existing conditions of projection, but also for the pur-
pose of establishing a set of recommendations regarding theater structures.

Many of the projects engaging the attention of the Committee have
been under consideration for a long time, some of them for several
years. The original plans for the projection room were drawn in
1930, and have been revised several times since. The study of screen
brightness has also continued for several years, concurrently with an
intensive study of all phases of the subject by the Projection Screen
Brightness Committee, which this year has been merged with the
Projection Practice Committee. In addition, a number of new proj-
ects have been undertaken, but the work on these has not progressed
sufficiently to warrant formal report. This report will be devoted
only to those subjects that have been developed to such a point as to
make a report worth while.

In prosecuting the work of the Committee it has been found ad-
visable from time to time to delegate specific projects to sub-commit-
tees appointed especially for the purpose at hand. The active sub-
committees at the present time are as follows :

Adoption of Projection Room Layouts as Standard ;
Projector Output and Screen Illumination

(including means of measurements) ;
Suprex Lamp Magnification Ratio;
Motor-Starting Time, Types of Take-Up ;
Technical Coordination;
Theater Structures;
Fire Hazards.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
10, 1937.

39

40 PROJECTION PRACTICE COMMITTEE REPORT [J. S. M. P. E.

It was with deep regret that the Committee learned of the death of
Rudolph Miehling on April 7th. Mr. Miehling had long been an
active member of the Committee, and had contributed very substan-
tially to its work. His loss is keenly felt by his friends and co-
workers.

SCREEN BRIGHTNESS

This subject was studied at length by the former Projection Screen
Brightness Committee and more recently by the present Projection
Practice Committee. The latter Committee at a meeting in Novem-
ber, 1936, approved the recommendation1 of the Projection Screen
Brightness Committee to the effect that the brightness at the center of
a motion picture screen be held within the range of 7 to 14 foot-lam-
berts. However, in taking this action, the Projection Practice Com-
mittee desires to qualify its approval by calling attention to the fol-
lowing considerations.

Many factors enter in practice to influence the physiological re-
action to light stimuli. Some of these were discussed in the Projec-
tion Screen Brightness Committee's report published in the August,
1936, issue of the JOURNAL. The Projection Practice Committee
cites the following factors as being of first-order importance in this
connection. The desirable screen brightness will depend upon the
density of the print; whether the picture is black-and-white or color,
the visual state of the audience upon entering the theater; the color,
width, and brightness of the screen frame and masking; the immediate
surroundings of the audience including the location; direction, color,
and intensity of the auditorium illumination ; and the color of the pro-
jection illumination source. In addition to the foregoing, there are
various other second-order factors.

Therefore, it will be appreciated that extreme conditions may
exist when 7 foot-lamberts may be more than sufficient, while at other
times 14 foot-lamberts might not be adequate. The report of the
Projection Screen Brightness Committee previously mentioned has
emphasized some of these thoughts. With this explanation of its
reservation, the Projection Practice Committee heartily concurs with
the findings of the former Committee and believes that their report
represents an important advance with respect to the subject.

The Projection Practice Committee will" continue its investigation
of the practical aspects of screen brightness in theaters, reporting
upon its findings as developments warrant.

July, 1937] PROJECTION PRACTICE COMMITTEE REPORT 41

MEASUREMENT OF SCREEN BRIGHTNESS

The function of the Sub-Committee of the Projection Practice
Committee, to which the study of this subject was assigned late in
1936, is to recommend specific apparatus and technic for studying the
practical illumination problems of the motion picture screen with
respect to the following :

(1) Brightness (upper and lower limits)

(2) Optimal screen size

(5) The effect upon the eyes of the viewer of the color characteristic of the
light-source

(4) Auditorium lighting conditions

(5) Resolution of detail and contrast value.

These items involve many factors; for example, both the intensity
and the color of the light reaching the viewer's eyes depend upon the
nature and the intensity of the light-source in the projector and the
reflection and color characteristic of the screen. The optimal size
of the screen, while primarily dependent upon the viewing distance,
must also be related to the available illumination. The net effect
upon the viewer's eyes will depend upon his state of fatigue, the am-
bient illumination, print density, and other considerations.

A study of the light intensity reaching the viewer will require re-
search involving viewing motion pictures at various intensities and
determining the effects produced thereby upon the eyes of a number of
viewers.

Relative to the selection of means for the measurement of illumina-
tion, both incident upon, and reflected from the screen, extended
study has indicated the virtual inability to repeat or check measure-
ments of this character when made with any of the recognized com-
mercial or laboratory measuring instruments now available. There-
fore, it is the view of this Committee that careful consideration should
be given to the characteristics required in a measuring device to be
suitable for making illumination measurements of projection light-
sources and light reflected from motion picture screens. A brief
summation of the more important considerations follows :

(2) Extensive comparisons have demonstrated that the response characteris-
tics of commercial light-sensitive instruments depart significantly from the re-
sponse characteristics of the average eye. Hence, spectral composition becomes
a variable which is likely to affect unduly measurements of such incident and re-
flected light.

(2) While in specific instances rather wide limits of measurement accuracy
can be tolerated in determining whether the conditions prevailing are satis-

42 PROJECTION PRACTICE COMMITTEE REPORT [J. S. M. P. E.

factory for an audience, it is believed that a tolerance limit of =*=5 per cent will be
required in meters or instruments used for measuring the light performance of
projection equipments in different theaters. The interest of one or more of the
commercial instrument manufacturers experienced in the development of il-
luminometers is being sought in an effort to bring about the development of a suit-
able meter.

Before such an instrument can be designed and manufactured,
specification requirements must be determined that will satisfy the
following considerations :

(1) The instrument shall provide, for the various types of light-sources en-
countered in projection rooms, consistent luminosity measurements that are
proportional to the visual effect of the light upon normal eyes.

(2) The meter shall be of such dimensions and rugged construction as to be
portable and capable of withstanding the handling necessary to its use.

(3) Obviously, the cost of the meter must be such as to promote its wide-
spread use throughout the industry.

Evidently the nature and present status of the problem as outlined
prevent drawing final conclusions at this time. Rather, the Com-
mittee proposes to canvass various individuals and companies having
potential interest in the problem with the object of organizing a
study in a logical and orderly fashion to gain the greatest possible
contribution for the common good.

It should be appreciated that the development required will prob-
ably prove costly and extensive. Some lengthy period of time may be
necessary in which to accomplish it. However, it is believed that
instruments capable of the performance desired will be produced
ultimately. One of the first requisites indicated by this situation is
the creation of a general interest among technical organizations
whose contributions will accelerate the development.

VISUAL TEST PATTERN FOR CHECKING SCREEN ILLUMINATION

The plan was suggested of designing and preparing a suitable film
containing a visual test pattern for projection in theaters to determine
whether a projected light falling upon the screen is satisfactory for
best viewing conditions. A study of the problem included a review of
the reports and papers published in the JOURNAL by various individuals
and by the Projection Screen Brightness Committee.

The consideration of the design of a test pattern included the follow-
ing factors:

(1) Weber-Fechner Law

(2) Range of print densities

July, 1937] PROJECTION PRACTICE COMMITTEE REPORT 43

(5) Type of test pattern

(4) Uniformity of illumination over the surface of the screen

(5) Effect of visual acuity of the observer upon use of the test pattern.

A plot of the just-perceptible brightness difference A B, expressed as
a fraction &.B/B (the Weber-Fechner fraction) has been published
in the JOURNAL2 for a natural pupil, with logio B (in foot-lamberts)
as abscissa and for a 3-degree field. This plot provides the means
for calculating the step densities of the test pattern. A film con-
taining these step densities would require the most accurate and
careful control of exposure and film processing. There is serious doubt
whether such control could be realized.

The range of densities to be covered should be taken from 3.2 to
0.19.3 These values are the highest -Dmax. and the lowest DmsLX
measured on a large number of release prints by the Projection
Screen Brightness Committee.

The type of test pattern must be one that would give the greatest
number of step densities at various absolute values of density for all
parts of the screen. Probably the most convenient would be one in
which the screen was divided radially from the center in either eight
or sixteen sectors. Each sector would have the density steps arranged
radially and the density steps of the different sectors staggered to
provide each portion of the screen with as many density steps as
possible.

Assume that it were possible to make a test pattern as described,
and in accordance with the Weber-Fechner Law, it would still be of
little use since the illumination on the screen is not uniform. The
brightest portion is at the center and decreases toward the margins.
The reduction of the marginal illumination depends upon the focal
length and type of projection lenses used. Hence the design of a test
pattern must of necessity take these facts into account, in addition to
many other variable factors.

Finally, no two observers would see the same results due to their
differences in visual acuity.

It was deemed advisable to include this negative report in the hope
that a different method of attack may be devised by someone which
will lead to a solution of this problem.

PROJECTION ROOM PLANS

As was previously mentioned, a partial revision of the projection
room plans published in the November, 1934, issue of the JOURNAL

44 PROJECTION PRACTICE COMMITTEE REPORT [J. S. M. P. E.

was made, and although the revisions were not sufficiently extensive
to warrant republication in the JOURNAL at this time, several thousand
copies of the revision were prepared in pamphlet form for distribution
to interested persons and organizations throughout the world. The
intention of the Committee was to distribute this report as widely as
possible in order to arouse a realization throughout the country of the
great lack of uniformity in regulations pertaining to motion picture
projection in theaters, and to attempt to enlist the assistance and so-
licit the suggestions and criticisms of law enforcement and fire preven-
tion departments of states and municipalities, so as eventually to be
able to draw up a model set of regulations that can be recommended to
the law-making bodies throughout the country.

Letters directed to the various States of the Union indicated con-
siderable misunderstanding regarding the purpose of the booklet, and
it was accordingly ruled by the Committee that the following caption
be imprinted upon the covers of the pamphlets in order to clarify the
situation :

"The material herein presented is recommended practice for new theaters,
and for alterations of existing theaters. It is not to be proposed as obligatory for
existing theaters."

This provision must be clearly appreciated in view of the fact that
certain differences exist between some of the recommendations con-
tained in the pamphlet and certain regulations of the National Fire
Protection Association. Further study of projection room and pro-
jection conditions is being conducted with the possible view of pre-
paring a set of practical regulations reconciling these differences.

PROJECTOR MOTORS AND TAKE-UPS

Difficulties encountered in projection with regard to motors and
take-ups are:

(a) Fast starting of the projector motor, which strains the gears
and damages the film;

(6) Irregular action of the take-up, with the result that jerks are
transmitted to the film, tending to tear the sprocket holes at the hold-
back sprocket. If the pad roller on the hold-back sprocket is of the
single-roller type and the jerk of the film is excessive, the film is likely
to be damaged and jerked from the sprocket entirely.

Jerking of the film may be caused either by rough action of the
clutch, slippage in the drive of the belt types, or slack in the drive in
either the belt or chain type of take-ups.

July, 1937 ] PROJECTION PRACTICE COMMITTEE REPORT 45

Either the adoption of the following specifications as standard or
the submission of them to the manufacturers of projection equipment
should help considerably in reducing the difficulties outlined above.

Motor-Starting. — Experience shows that a starting time of two to
three seconds seems to be quite satisfactory. The acceleration of the
equipment from zero to full speed should be approximately steady,
and under no circumstances should have a break in the speed-time
characteristic. This latter point is mentioned because the use of a
resistor in the starting winding for slow starting, and short-circuiting
this resistor as the motor comes up to speed, is likely to cause a jerk
in the equipment at the time the resistor is shorted.

Take- Ups. — The design of take-ups should be such that the pull of
the film is steady at all times, irrespective of the amount of film upon
the take-up reel.

It is preferable to use double pad rollers on the hold-back sprocket
to insure that the film stays upon the sprocket at all times.

Projectionists using the equipment can reduce film damage by mak-
ing certain that the film is not slack between the take-up reel and the
hold-back sprocket before starting the projector.

SOUND SCREENS

The accepted practice and requirements with regard to the trans-
mission of sound through motion picture screens have not undergone
any appreciable changes since they were established during 1930 and
1931. The only major difference refers to the losses allowed at the
higher frequencies.

The screens in common use at the present time are those in which
the sound waves are transmitted through the air spaces in the screen
material. These air spaces may be either the pores of the material or
perforations punched into the material.

Because of optical characteristics of the screen material, the per-
forations or air spaces should be as small as possible and the number
of perforations a minimum.

As a result of tests, it was decided to limit the aggregate open area
for the screen to 7.5-10.0 per cent of the total screen area. The ratio
of the thickness of the screen material to the area of a single opening
should be very small, because the air in the individual air passages
presents a mass reaction to the flow of sound energy.

The frequency response of a screen enters into the determination of
its suitability from an acoustical standpoint. No serious trouble is

46 PROJECTION PRACTICE COMMITTEE REPORT [J. s. M. P. E.

experienced with regard to the low-frequency response but a drop
occurs at the higher frequencies.

Losses at various frequencies were limited as follows :

4.5 decibels at 10,000 cps.
2.5 decibels at 6000 cps.
0.5 decibels at 1000 cps.

Each of these figures represents an average value taken from mea-
surements having no variations due to testing procedure that exceed
plus or minus 2 db.

On the whole it is quite difficult to set definite limits for screen
transmission to cover all possibilities, but if the tolerances given above
are adhered to, efficient results will be obtained.

THEATER SURVEY

In order to obtain information that would assist in the study of
screen brightness and various other matters, such as projection
angles, seating areas, general lighting, in addition to a number of
projection and screen characteristics, a chart was drawn up containing
skeleton diagrams of the vertical and horizontal plans of a theater.
Several thousands of these charts have been distributed among a
number of large companies of the industry whose engineers are assist-
ing in obtaining the dimensions requested on the chart. A reproduc-
tion of the chart is shown in Fig. 1. Accompanying the charts dis-
tributed were letters describing its purpose.

The theaters covered in the survey include all classes, both as to
size and general construction, and there will be sufficient representa-
tion of the entire industry to permit a very reliable analysis of condi-
tions to be made. Instead of mailing the charts directly to the man-
agers of theaters, it was felt that the results would be more reliable if
the measurements were made and the charts filled out by men experi-
enced in such work. Accordingly, the field men and the management
of RCA Manufacturing Co., International Projector Corp., Electrical
Research Products, Inc., National Carbon Co., Inc., Forest Electrical
Co., Bausch & Lomb Optical Co., and National Theater Supply Co.
are all to be thanked for their cooperation. In addition, a number of
charts were distributed to the delegates at the Convention of the
M. P. T. O. A. at Miami in March and the additional information de-
rived therefrom will probably be very helpful. As it will probably
require consideration time to make a thorough analysis of charts that

July, 1937] PROJECTION PRACTICE COMMITTEE REPORT

47

are returned, it may not be before the October Convention of the
Society that the Committee will be able to render a report on its
findings.

SOCIETY OP MOTION PICTURE ENGINEERS
Hotel Penn.ylianla N e • York City

SURVEY
Of MOTION I'ICTIIRK
THEATHK STRUCT HIES

envelope provided.

ORCHE3TP4 FLOOP PLAN

LONGITUDINAL SECTION

Question No, 1.

Uuestlon No. 5.

Dimension A should be klilte Picture WIDTH.

AC Volts

Dimension L should be Width of Proscenium

Question No. 8.

*ie«_lion «o. 3.

Question No. 7.

B-Balcony
Total

Question No. 8.

Question No. 3.

of theatre.
Question No. 9.

A- Beaded or metallic

i - lltlier-Uescrlbe

Question No. 4.

Check type of proje tlon llgiit source In use.
A- Lo« Intens ty Anps.

11- High Inten ily
1) HlKh- o« (Heflector)

2) Conde ser Type
3) Supre

Fora ~~~

H- —

0 A.C. Arc

riojicTioi rocTicc COHHITTK

FIG. 1. Theater survey chart.

With the information thus obtained, the Committee hopes even-
tually to be able to construct plans for various types of theaters, just
as they have been able to construct plans for projection rooms.

48

PROJECTION PRACTICE COMMITTEE REPORT [J. S. M. P. E.

These plans are to include schedules of screen sizes, screen brightness,
and other matters of importance to architects and others engaged in
building new or altering existing theaters.

MUTILATION OF FILM

In view of the fact that devices have been placed upon the market
by means of which projectionists may place upon films cue marks for

change-overs, the following reso-
lution was adopted by the Com-
mittee at its meeting in January :

Guided Edge

.0.020"

"The Projection Practice Committee
of the Society of Motion Picture Engi-
neers does not approve any structural
modification, injury, or mutilation of
the Standard Release Print by the
projectionist, and views with disfavor
the sale of devices capable of causing
physical damage to the film for cue
marks or the like. The Committee
regards cue-marking as a function ex-
clusively of the laboratory."

PICTURE APERTURES

Since the adoption of the
standard camera and projector
apertures by the industry several
years ago, these standards have
not fulfilled the requirements for
which they were created, due to failure to take into consideration
the masking at the theater screen.

To overcome objectionable blocking out by the screen masking of
important parts of the photographed action, it is recommended that
action being photographed be limited to an area 0.005 of an inch
smaller on all sides than the dimensions of the standard projector
aperture.

The following will outline in general the differences between the
camera and projector apertures:

Camera 0.868 ± 0.002 inch wide
0.631 ± 0.002 inch high
0.744 =*= 0.002 inch center-line from guided edge.

FIG.

2. Recommended area
photographed action.

of

July, 1937] PROJECTION PRACTICE COMMITTEE REPORT 49

Projector 0.825 ="= 0.002 inch wide
0.600 =*= 0.002 inch high
0.738 ± 0.002 inch center-line from guided edge.

It has been found from experience that, on a 9 by 12-foot screen at
an angle of projection of approximately 15 degrees, a 1-inch masking
around the screen into the projected picture has proved sufficient to
assure proper projection.

This 1-inch masking represents a decrease of 0.005 inch approxi-
mately on each side of the projector aperture, or an aperture 0.815
inch wide by 0.590 high, 0.738 ± 0.002 inch from center-line to guided
edge (Fig. 2).

The Committee recommends, in view of the facts given above
and in order to avoid loss of portions of the picture, that cameramen
and studio laboratories provide their camera-focusing devices and
view-finders with a working ground-glass having a rectangle of the
conventional thin black line corresponding to the dimensions 0.815 by
0.590 inch, as an aid to the cameraman in composing his picture.

The Committee also recommends that a minimum masking or
overlapping of the projected film image upon the screen be established.
For example, on a 9 by 12-foot screen the masking should not
overlap the projected picture more than one inch on each side; for
smaller or larger screens this masking or overlapping on each side
should be of the same approximate ratio.

H. RUBIN, Chairman

J. O. BAKER A. N. GOLDSMITH E. R. MOWN

T. C. BARROWS A. GOODMAN M. D. O'BRIEN

F. E. CAHILL H. GRIFFIN G. F. RACKETT

J. R. CAMERON S. HARRIS F. H. RICHARDSON

A. A. COOK J. J. HOPKINS B. SCHLANGER

J. K. ELDERKIN C. F. HORSTMAN C. TUTTLE

J. J. FINN D. E. HYNDMAN J. S. WARD

R. R. FRENCH J. J. KOHLER V. A. WELMAN

E. R. GEIB P. A. McGuiRE A. T. WILLIAMS

REFERENCES

1 Report of Projection Screen Brightness Committee, /. Soc. Mot. Pict. Eng.,
XXVII (Aug., 1936), No. 2, p. 127.

2 /. Soc. Mot. Pict. Eng., XXVI (May, 1936), No, 5, p. 517. (See Fig. 3.)

3 /. Soc. Mot. Pict. Eng., XXVI (May, 1936), No. 5, p. 551. (See Table II.)

REPORT OF THE COMMITTEE ON EXCHANGE PRACTICE*

Summary.— With the recent reorganization of the Committee representation was
effected from all the important exchange companies, in addition to the theater and
laboratory branches of the industry, which gives the Committee close contact with all
the important factors in which it may at any time be interested.

The attention of the Committee is restricted to the physical handling of film in ex-
changes, questions of safety and fire prevention, technic and supervision of inspection,
uniformity of exchange practice, and the like.

Projects have been initiated for drawing up plans for an ideal exchange, for pre-
paring an instructional booklet for exchanges, and for producing a descriptive film
to supplement the booklet.

The Committee on Exchange Practice was originally formed in
July, 1932, under the Chairmanship of Mr. Trevor Faulkner. Regu-
lar reports were submitted to the Society each year, a list of which is
appended to this report for reference.

At the beginning of 1937 a reorganization of the Committee was
effected, the new members consisting of the heads of the various
New York City Exchange Departments, so that a closer contact
could be maintained with the very branch of the industry that would
be most interested in the work of this Committee. In order to
show this relation, the list of members of the Committee is given
herewith, together with their company affiliations :

A. W. SCHWALBERG, Chairman (Warner)

O. C. BINDER ( Universal) H. A. MERSAY (20th Century-Fox)

A. S. DICKINSON (M. P. P. D. A .) N. F. OAKLEY (Dupont)
G. K. HADDOW (Paramount) H. RUBIN (Paramount)

H. C. KAUFMAN (Columbia) A. SCHUBART (R. K. O.)

J. S. MACLEOD (M-G-M) J. H. SPRAY (Ace Labs.)

It is with deep regret that the Committee records the death of
one of its most active members, J. P. Skelly, on March 8, 1937.

It will be noted that in addition to having representation among
the various large companies, the Conservation Department of the
M. P. P. D. A. through Mr. Dickinson, the Laboratory branch of the
industry through Mr. Spray, as well as a film manufacturing com-
pany through Mr. Oakley, are represented.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
12, 1937.
50

EXCHANGE PRACTICE COMMITTEE REPORT 51

During the past season meetings of the Committee have been held
every month at the offices of the M. P. P. D. A. Minutes of the meet-
ings have been prepared and circularized by the Secretary of the
Committee, Sylvan Harris, and it is the plan of the Committee to
continue its meetings regularly during the entire year. This, the
first report of the new Committee, will be followed in due course by a
detailed description of the Committee's accomplishments at the next
Convention in October.

The first meeting of the new Committee was held on February 25th,
at which time the agenda and scope of the Committee were estab-
lished. The attention of the Committee is restricted to the physical
handling of film and not to subjects relating to advertising accessories,
accounts, sales, or the like. Other problems facing the Committee
refer to safety and fire prevention, the technic and supervision of
inspection, methods of "processing" film, and uniformity of exchange
practice.

The question of uniformity of exchange practice and technic have
been receiving the close attention of the Committee for some time,
particularly with reference to the relation between the laboratory
phase and the projection phase, referring to the state in which film
is received by the exchanges from the laboratories and sent by the
exchanges to and received from the theaters. In this connection, it
is important to note that the Chairman of the Projection Practice
Committee of the SMPE, Harry Rubin, has been made a member of
this Committee.

Considerable attention has been given to the subject of rewinding
films in exchanges and the manner of making patches. It was the
decision of the Committee that in the interests of uniformity it would
be best to supply films to the theaters wound with the heads out,
despite the fact that this would lead to a slight problem in Chicago,
in view of the requirement in that city that the projectionists use
14-inch reels, making it necessary to rewind the film from the reels
supplied by the exchanges. Exception must therefore be made in
the Chicago area, in supplying the films wound with the tails out.

Steps have been taken to improve the uniformity of printed mate-
rial accompanying films shipped out by exchanges, in respect to reel-
bands, labels, etc., the idea being to make the information contained
thereon more uniform and explicit.

A plan has been formulated to prepare an instruction booklet,
under the auspices of the Committee, for distribution among ex-

52 EXCHANGE PRACTICE COMMITTEE REPORT [J. S. M. P. E.

changes, which would describe in more or less detail the proper way
to inspect and handle film. Such a booklet was prepared some time
ago for use in Paramount exchanges, but the plan is to prepare a
more up-to-date and complete guide for the exchange personnel than
was available in the Paramount booklet.

Steps have been taken also to draw up plans for an ideal exchange,
probably in a form somewhat similar to the plans drawn up by the
Projection Practice Committee some time ago for motion picture
projection rooms. These plans will describe, in general terms, the
recommended construction of the exchange; specifications for the
equipment ; and proper method of operation, including housekeeping
and general maintenance. The plans will also contain general
information relating to the problems of supervision, working condi-
tions, the advantages of avoiding confusion and noise, the impor-
tance of adequate light and ventilation, cleanliness, etc.

Another project that will undoubtedly turn out to be of great
importance to the exchange branch of the industry is that of preparing
a demonstration film, under the supervision of the SMPE Exchange
Practice Committee, which would show the proper procedure to be
followed in inspecting and handling film in the exchanges. This film
will complement the instructional booklet described above. The
scenario for the film is now being prepared, and it is probable that
shooting will begin within the next month or so. The purpose would
be to provide prints of the film to exchanges, as needed, for showing
at their various branches in order to instruct their employees. How
often such showings will be necessary will, of course, depend upon the
needs of the exchanges and upon the turn-over of their personnel.
The film will tell a running story, the comments being made either
in the form of a running narrative or as remarks by the various actors
in the picture.

The items described are the more important ones facing the Com-
mittee. In addition, however, there are a number of other items
that do not warrant a report at this time in view of the fact that work
upon them is just being initiated. However, it is expected that by
the time of the Fall Convention in October a very complete report
of the year's work will be available; and in view of the fact that the
members of the Committee are those in charge of the various ex-
change circuits, it is anticipated that the improvements in procedure
and uniformity that will be agreed upon by the Committee will be
put actively into effect in the exchange branch of the industry without

July, 1937] EXCHANGE PRACTICE COMMITTEE REPORT 53

delay. However, close collaboration with other branches of the
industry is desired in view of the fact that the exchange branch repre-
sents only one link in a long chain, and the procedure adopted in the
exchanges is dependent to a large extent upon the materials supplied
to the exchanges and the manner in which the film is handled in the
theaters.

REFERENCES
Reports of the Exchange Practice Committee:

/. Soc. Mot. Pict. Eng., XX (March, 1933), No. 3, p. 199.
Ibid., XXH (May, 1934), No. 5, p. 332.
Ibid., XXV (Nov., 1935), No. 5, p. 462.

REPORT OF THE COLOR COMMITTEE*

Summary. — The Eastman perforation, although adopted by the Society as a
standard for positive and negative film, has certain disadvantages for use in con-
nection with color processes and for background projection. The reasons for these
limitations are analyzed, and a proposal is made that the important advantages of
the Eastman filleted rectangular shape be retained in a perforation, the dimensions
of which are the same as those of the Bell & Howell perforation. Such a perfora-
tion would fit existing Bell & Howell registering pins.

The use of a photocell having most of its sensitivity outside the visible spectral region
imposes an added burden to those "working upon color sound processes. Search is
urged for a cell that would have all the advantages of existing caesium cells but with
its chief sensitive response in the visible range.

The term "Direct Color Developer Process" is recommended for a color process
wherein non-diffusing color-formers in the emulsion (multiple-layer) combine with
the oxidation products of the developer to form insoluble dyes. A process of this type
was introduced recently by Agfa.

Perforation Standards. — Prior to 1930, the industry was using what
is known as the Bell & Howell perforation for both negative and posi-
tive stocks. The overall dimensions of this perforation are 0. 1 10 inch
wide by 0.073 high, and the shape is such that the rounded ends of the
perforation lie upon a circle.

In the fall of 1930, the Society adopted a new standard perforation
for positive film only, the shape of which is a filleted rectangle of di-
mensions 0.110 inch by 0.078. This shape and size are usually referred
to as the Eastman perforation, because it was introduced by the East-
man Kodak Company some years earlier. This new standard for
positive film has been adopted by the black-and-white industry gen-
erally; however, it has not been adopted by any commercially oper-
ating color process. All color prints being commercially produced
today have the old Bell & Howell standard perforation. The reason
is, of course, the necessity in present-day color processes of transfer-
ring accurate register from negative to positive by means of regis-
tering pins. This means that at least the overall dimensions of the
perforations in negative and positive must be the same.

In November, 1934, the Society adopted the Eastman perforation

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received April
15, 1937.
54

REPORT OF COLOR COMMITTEE 55

as standard for negative as well as for positive stock but there is no
indication, either here or abroad, that this new standard for negative
stock will actually be accepted; in fact, it appears that it will not be
accepted. There are several reasons for this. For example, steadi-
ness in background projection requires transfer of registration of pic-
tures with respect to sprocket holes from the negative to the print,
and the use of registering pins in the projector. It is universal prac-
tice in the black-and-white industry to use Bell & Howell perforations
even in the positive prints used in this type of work. Much of the
negative material used in background projection conies from "stock
shots," all of which, of course, already have the Bell & Howell perfora-
tions. A third reason is that the confusion that would result during
the change-over period might result in cases wherein film containing
the small perforations encounters large-size pins either in camera,
printer, or projector. In such a case, jamming and damage to the
film would result. While it might be possible to re-perforate the old
negative to the new standard, and, further, so to organize the period
of transition as to minimize trouble, the fact remains that the industry
has taken no step to adopt the Society's recommendation on Novem-
ber, 1934. The Society now finds itself in the rather unfortunate
position of having approved, in November, 1934, a standard that the
industry has refused to accept in practice. From the point of view of
the present-day color processes, even the standard adopted in 1930
for positive stock is impracticable.

The reason for adopting the increase in the vertical dimension in the
case of the Eastman perforation was to allow additional clearance on
projector sprockets to compensate for film shrinkage; but this diffi-
culty has been minimized in the intervening years by the introduction
of film bases of less shrinkage than those that were in use at the time
the Eastman perforation was promulgated. Furthermore, the sound
revolution has caused a very great increase in the care taken inmechani-
cal maintenance of equipment in the theater projection room.

Now it is believed, and such tests as have been made substantiate
the belief, that the very definite and important advantages of the fil-
leted rectangular shape can be retained in a perforation whose dimen-
sions are the same as those of the Bell & Howell perforation and will
consequently fit upon existing Bell & Howell perforation registering
pins. Such a solution of the problem has previously been urged by
Mr. Howell.

While the cost of a change of standards is always great, it never

56 REPORT OF COLOR COMMITTEE

grows any less with time, and there is, of course, a not inconsiderable
current expense to maintain two standards. In view of the fact that
such standards as have previously been adopted have been found to be
impracticable both for black-and-white and, especially, for color, the
Color Committee feels that the Society, through its Standards Commit-
tee, would do well to examine carefully the possibilities and advan-
tages of a new universal standard perforation that would be practi-
cable.

Photocell Sensitivity. — The Color Committee would like to call the
attention of those working in sound to the fact that the use in the pro-
jector of a photoelectric cell such as the caesium cell, having most of
its sensitivity outside the region of the visible spectrum, requires that
color processes deal not only with the visible spectrum but also with
the added region in which the photocell is sensitive. This imposes a
further burden upon those working in color. Their problems would
be considerably simplified were the sensitivity of the photocell con-
fined to the visible spectrum. The sound men themselves would gain
an advantage also in such a case, due to a simplification of the design
and accurate focus setting of the optical system in the reproducer.
We do not mean in any way to urge a return to the potassium cell
that was in use prior to the advent of the caesium cell but rather to
urge the search for a cell having all the advantages of the caesium cell
but with its principal sensitivity within the visible range. In other
words, the Color Committee believes that the ideal photocell for the
projector has not yet been developed and it would urge the sound men
to seek it.

Further Classification of Color Processes. — A further classification of
types of color processes is needed to take care of the process recently
introduced by Agfa. In this process, non-diffusing color-formers re-
side in the several emulsion layers. When the film is developed in a
coupler-developer these color-formers combine with the oxidation
products of the developer to form insoluble dyes. The phrase, "direct
color," has been considered as descriptive of this process, but such a
phrase might also apply to a bleach-out process. The recommended
phrase, therefore, to describe the new process is "direct color developer
process."

J. A. BALL, Chairman

W. H. CARSON C. H. DUNNING A. M. GUNDELFINGER

O. O. CECCARINI R. M. EVANS H. W. MOYSE

REPORT OF THE NON-THEATRICAL EQUIPMENT
COMMITTEE*

Summary. — A resume is presented of correspondence conducted with the British
Institute of Cinematography. The report of this organization is abstracted as follows:
(1) A theoretical analysis of the light losses in a projector rising direct illumination
is made, showing that for every 100 lumens emitted by the lamp, only 2.43 lumens
find their way through the projection lens; (2) it is suggested that unit intensity be
used as a method of comparison between one projector and another and that 1 foot-
candle be regarded as an average value for home use and 4 foot-candles for small audi-
toriums.

Objection is taken by this Committee to the latter proposal, and the opinion is ex-
pressed that the suggested values are too low. A satisfactory intensity should cover
projection of adequate quality.

Attention of the Society is directed to the matter of standardizing the procedure
for the determination of total screen lumens.

This Committee is investigating the German recommendations
concerning standardization of camera and projector sprockets, prin-
cipally 16-mm., with a view of passing on recommendations to the
SMPE Standards Committee for further consideration.

Additional work is being done in the matter of establishing a sat-
isfactory basis upon which to rate 16-mm. projector performance.
In this respect, some correspondence has been conducted with the
British Institute of Cinematography in connection with their initial
report on the same subject, which appeared in January, 1937. l
It is felt that the report is sufficiently important to warrant repeating
its essentials:

"In a projector, a source of light is enclosed in a lamp house having
an opening in which is fixed a condenser ; usually, in addition, a re-
flector is mounted diametrically opposite the condenser. The light
escaping through the condenser passes through a gate, a shutter, and a
projector lens. Assuming that the projector is running at normal
speed, with no film in the gate, what proportion of the light emitted
from the lamp escapes from the projection lens? Consider the ob-
vious sources of light loss, working from the projection lens back to
the lamp.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.

57

58 REPORT OF NON-THEATRICAL COMMITTEE [J. S. M. P. E.

"(1) The Lens consists of a number of glasses, all of which absorb
a certain amount of light in themselves and the combination has an
effective aperture which controls the amount of light passed.

"(2) The Shutter. Assume a two-bladed shutter with 90-degree
blades. The light passing to the projection lens is cut by one-half
during each revolution of the shutter, so that 50 per cent of the light
output is lost. This is a necessary loss and varies according to the
type of shutter.

"(«?) The Gate is rectangular in shape and must be evenly illumi-
nated to the corners so that the diameter of the circle of light passing
from the condenser must be at least equal to the diagonal of the gate.
The loss here is therefore equal to the difference between the area of
the gate and the area of the circle of light whose diameter is equal to
the gate diagonal. This loss amounts to no less than 40 per cent.

"(4) The Condenser is of thick glass and absorbs its proportion of
light

"(5) The Lamp House. The diameter of the condenser is condi-
tioned by the diagonal of the gate and its distance from the gate.
Reverting to our consideration of the candle inside a sphere, it will be
seen that since the opening in the sphere, or enclosure, is already con-
ditioned, the light-source must be brought as near as possible to the
condenser so that the opening in the equivalent sphere is as large a
proportion of its total area as possible. This, in turn, is conditioned
by the heat generated by the lamp, because the greater the heat the
larger must be the diameter of the glass tube, and hence the greater
the distance of the filament from the condenser. The most efficient
reflector is a polished silver surface, but, as this surface deteriorates,
a silvered mirror is preferable over a period of time and will reflect
not more than 75 per cent of the light incident upon it.

"Taking these matters into consideration, and assuming that the
whole of the horizontal candle-power can be directed at the condenser,
we have, very roughly, one-twelfth of the lamp lumens plus 75 per
cent of this figure; i. e., all that we can expect to present to the con-
denser is, very roughly again, some 15 per cent of the total lumens of
the lamp. This upon the further assumption that the square of the
distance from the lamp filament to the condenser is not numerically
greater than the effective area of the condenser opening.

"Adding up these sources of loss, it is not surprising, therefore, to
find that the efficiency of a projector measured in terms of the ratio of
lumens output to lumens input to the lamp house is only of the order

July, 1937] REPORT OF NON-THEATRICAL COMMITTEE 59

of 2 per cent. Hence the comparison of projectors by means of their
true measured efficiency will not convey a great deal, and it is, there-
fore, advisable to consider some other method.

"Only projectors with direct lighting have been considered above.
Those of the indirect type, where the lamp house is at the side of the
machine and the light issuing from the condenser is reflected at right
angles to the gate, have an additional light loss due to absorption by
the mirror. A prism giving total reflection does not entirely over-
come this loss, as there is still absorption taking place in the glass. In
view of the other losses, however, this loss is not serious.

"A summary of the losses in a projector using direct illumination
can be demonstrated in the following way. The figures given do not
refer to any particular type or make of projector, but represent a
purely theoretical case.

"For every 100 lumens emitted by the lamp:

15 lumens arrive at the condenser surface, including light reflected by the
mirror;

13 . 5 lumens find their way through the condenser;
4.5 lumens find their way through the shutter;
2.7 lumens find their way through the gate;
2.43 lumens find their way through the projection lens.

"It should be appreciated that with a given projector, the true
efficiency can be increased in two ways: by the use of a projection
lens of greater effective aperture, and by the use of a shutter having a
shorter period of cut-off. The actual light output can also be in-
creased by using a higher-wattage lamp, or a lower-voltage lamp of
the same wattage, this latter giving a greater number of lumens per
watt. But increased wattage in the same lamp house, although giving
increased light output, generally does so at the expense of efficiency.
It is usual to express the overall efficiency of a projector in screen
lumens per watt, and this figure varies from about 0.06 for 8-mm.
machines to 0.6 for 16-mm. machines.

THE RATING OF PROJECTORS

"In determining a suitable criterion of screen illumination, consider-
ation must be given to the practicability of this criterion and to the
manner in which the customary illumination of screens is affected
thereby. It is customary in the home, on the one hand, to arrange the
projection room to be completely dark if possible, and in the profes-
sional auditorium, on the other hand, it is usually a matter of law to

60 REPORT OF NON-THEATRICAL COMMITTEE [J. S. M. P. E.

have sufficient lighting in the auditorium to enable the audience to
see its way out in emergency. Conditions in the home and in the
cinema differ in two respects:

(a) The home auditorium can be made completely dark, the cinema can not ; and

(b) The type of film used in the home is usually of the reversal type and
dense, whereas in the cinema it is of the positive type and, by comparison, thin.

"It is not beyond the bounds of probability, therefore, that the
additional light required by reversal film is offset by the additional
light required in the theater by virtue of the fact that stray emergency
lighting reaches the screen and tends to dull the picture.

"The criterion suggested is that of an intensity of one foot-candle
at the surface of the screen when the screen is illuminated by light
projected through a piece of film of perfect transparency. This
means that when a film containing a grading from perfect transpar-
ency to perfect opacity is projected onto a screen, the light at the sur-
face of that screen varies from 0 to 1 foot-candle. It may be said
here that if the screen were evenly lighted by stray light to an inten-
sity of 1 foot-candle, then the variation of light would be from 1 to 2
foot-candles, giving a duller picture, but still visible. The amount of
light reaching the eye from a screen so illuminated depends upon the
reflecting power of the screen, and the reflecting powers of commercial
screens will be the subject of a further investigation. In the mean-
time the suggested criterion can be taken to refer to an average screen
3uch as is used in the home, having an average reflecting power over a
fairly narrow angle.

"At first sight this intensity of 1 foot-candle appears very low, but
it should be remembered that it is being applied in a special case.
From a psychological point of view, attention is being focused upon a
small area, and this represents only a small section of the total area
that would be taken in by the eye if all objects in the total angle of
view at that distance were illuminated. It is probable that the eye is
called upon to do less work when focused at one distance only upon a
two-dimensional object, and requires less stimulation of light than
when constantly changing focus and direction and measuring dis-
tances, as is the case normally. It is suggested that unit intensity be
used as a method of comparison between one projector and another,
and that this intensity of 1 foot-candle be considered as an average
value for home use and that an intensity of 4 foot-candles be con-
sidered as an average value for small audiences including educational
use. This is more or less within present practice.

r, 1937] REPORT OF NON-THEATRICAL COMMITTEE 61

"It is proposed to classify projectors according to the size of screen,
rhich will give the intensities mentioned above.

"Before proceeding to the method of measurement and classifica-
tion it will be of interest to examine the claims put forward for some
of the well-known projectors on the market today. The screen lu-
mens given for the 16-mm. projectors are those published by the
makers and those given for the 9-mm. projectors are the results of tests.

"Messers. Siemens claim that their standard projectors have been
used to show a 16-ft. picture (0.68 foot-candle) to an audience of over
2000 people, and speak of 21 lux (1.95 foot-candles) as an 'extraor-
dinary light value.' If we exclude the 13-ft. guaranteed picture of
the Agfa, which refers to a white screen, and assume that the other
claims presuppose the use of the best type of beaded screen, then the
intensities vary from 0.32 to 0.84 foot-candle, and our requirements
of 1 foot-candle on an average screen appears to be reasonable.

"R. F. Mitchell2 has suggested a standard of 6 foot-candles as a
basis of classification, but this would appear to be impracticably high
in view of the present output limitations of substandard projectors,
since one has yet to hear of a 16-mm. projector with an output as high
as 300 screen lumens,* and even this figure would limit the size of a
screen to a maximum width of 8 feet. This was only a suggested
standard, however, and he also said that the corresponding screen
sizes could be doubled if necessary, i. e., an intensity of 1.5 foot-candles.
A point of interest, however, is that Mr. Mitchell stated in the discus-
sion in a previous paper that it was quite usual to show a 12-ft. or
14-ft. picture to an audience of 1000 or 2000 people with quite satis-
factory results when using a 750- watt lamp. Now, a Bell & Ho well
750- watt projector with an //1. 65 lens gives about 210 screen lumens,
so presumably the audience was satisfied with intensities of 1.95 and
1.43 foot-candles."

The Chairman of this Committee has objected to the interpretation
of this low intensity as being satisfactory, because of the fact that
many 16-mm. projector manufacturers advertise the possibility of
showing large-size pictures. A careful definition of the word satis-
factory has been suggested: "Too often we tend to use this word to
cover projection of minimum suitability, whereas really it should
cover projection of adequate quality." The attention of the British
Institute has also been called to the various papers that appeared in

* Such a machine is available.3

62

REPORT OF NON-THEATRICAL COMMITTEE

the May, 1936, JOURNAL, and their reply is being awaited with con-
siderable interest.

The Committee would like to call the attention of the Society mem-
bers in general to the matter of standardizing the procedure for de-
termining total screen lumens. The lack of an approved method in-
troduces sufficient differences as to hamper, if not prevent, satis-
factory progress of this rating procedure.2 This Committee is co-
operating with the Projection Practice Committee and Standards
Committee in furthering the establishment of these desirable recom-
mendations.

R. F. MITCHELL, Chairman

D. P. BEAN E. C. FRITTS R. C. HOLSLAG

F. E. CARLSON H. GRIFFIN J. H. KURLANDER

W. B. COOK J. A. HAMMOND A. SHAPIRO

H. A. DEVRY A. F. VICTOR

REFERENCES

1 "The Performance and Classification of Substandard Projectors," J. Brit.
Inst. Cinemat., (Jan., 1937), No. 1, p. 6.

2 MITCHELL, R. F.: "Non-Theatrical Projection," J. Soc. Mot. Pict. Eng.,
XXXI (Oct., 1935), No. 4, p. 314.

J MITCHELL, R. F., AND HERD, W. L.: "1000-Watt 16-Mm. Filmosound
Projector," J. Soc. Mot. Pict. Eng., XXVII (Oct., 1936), No. 4, p. 440.

REPORT OF THE MEMBERSHIP COMMITTEE*

Summary. — The membership of the Society is growing steadily at the net rate of
25 to 30 members a month, the present (April 30, 1937) membership being 1283, with
30 applications pending. The broadening of the membership to include all the
important countries of the world, in addition to the domestic membership, is indicative
of the widening activities of the Society in international motion picture affairs.

The growth of the membership, although not spectacular, this past
year has nevertheless been steady and quite satisfactory. During
1936 the net increase was approximately 25 new members a month.
Since January 1, 1936, 79 new members have been admitted, 18 old
members reinstated, and 30 new applications are pending, making a
total of 127, or approximately 32 a month.

The net figure, however, is less than that, because of the fact that,

as every year, there are a few resignations, and this year so far there

have been five deaths. The net, however, as stated, is very close to

25 a month.

The total membership at the present moment (April 30) consists of :

Honorary 7

Fellows 140

Active 328

Associate 808

Total 1283

Applications

Pending 30

Total 1313

This figure may be reduced somewhat by the middle of the year,
because at that time members who have not paid their dues for the
current year will become delinquent. It is expected, however, in
view of the general improvement in conditions, that the number of
delinquents this year will not be as great as that of last year, so that
by the end of 1937 it is anticipated that the net membership in good
standing will be well over 1400.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.

63

64 REPORT OF MEMBERSHIP COMMITTEE

It is particularly interesting to note that the foreign membership of
the Society is increasing as rapidly as the domestic membership.
This is probably due in part to the broadening of the Society's activi-
ties through its relations with the foreign standardizing bodies and
other motion picture engineering societies.

A similar increase may be noted also with respect to non-member-
ship subscriptions. For several years the number of non-member
subscriptions averaged very close to 200. During the past two years,
however, the number has increased to 364, the net increase during the
past four months alone being 66. Many of these non-membership
subscriptions are held by the libraries of large research and industrial
organizations, and as noted above in connection with membership,
the increase in non-member subscriptions in foreign countries is par-
ticularly interesting.

Although the situation is very promising, and the membership and
non-member subscriptions have reached new high peaks, it is the de-
sire of the Membership Committee that there be no relaxation of
effort to increase the membership further. The Society does not by
any means cover the entire field adequately, and there are many per-
sons actively engaged in the motion picture field, even in such a center
as Hollywood, who could well become members of the Society, to the
interests both of the Society and themselves. The Membership and
Subscription Committee seeks the assistance of the entire member-
ship of the Society in this work.

E. R. GEIB, Chairman

TONING POSITIVE FILM BY MACHINE METHODS*
J. M. NICKOLAUS*

Summary. — A description of the toning of the entire release of the Metro-Goldwyn-
Mayer production "The Good Earth," using a modified developing machine,

Toning a motion picture positive film is an art that has been nearly
forgotten. For the past decade very little, if any, toning has been
done. The inception of sound photography with its many compli-
cated problems probably had a great deal to do with it, but with
the advances that have been made, not only in sound photography
but also in laboratory processing, it is not inconceivable that this art
might be partially revived.

Many of the emotional moods that motion pictures seek to portray
can not always be depicted to their full extent by the normal gray
tone of black-and-white photography, since gray tones can have a
very sobering effect upon the observer. While gray no doubt en-
hances certain moods, there are many instances where color of some
sort would enhance the mood and thereby produce a more striking and
favorable reaction upon the observer. Much of the early work in
motion pictures made use of color effects produced by the use of tints
and tones, either separately or in combination. Every so often a
picture is made in which definite mood effects are to be depicted that
could be greatly strengthened by the use of some color medium. The
choice of the color, as well as the medium, requires very definite plan-
ning.

When consideration was given by Metro-Goldwyn-Mayer to the
picture The Good Earth it was felt that normal black-and-white
photography did not convey the desired mood satisfactorily. Search-
ing for a means to produce the desired effect the subject of toning the
positive print was given consideration, and after much experimental

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 11, 1937.

k* Metro-Goldwyn-Mayer Studios, Culver City, Calif.

65

66 J. M. NICKOLAUS [J. S. M. P. E.

work a solution of the problem was arrived at, as will be described.
One of the reasons why it was felt desirable to present the data was
the fact that to the best of our knowledge this is the first complete
major release to be toned in its entirety, and, furthermore, it is the
first picture to be so toned in a modern developing machine.

It should not be presumed that because the release prints of The
Good Earth were completely toned, there is a desire on the part of the
studio to tone other pictures indiscriminately. It must be remem-
bered that the decision to tone the prints of this picture was not ar-
rived at with any thought in mind of eliminating color photography.
It stands to reason that it is extremely difficult to find a story that has
been photographed that is so completely adaptable to toning as was
this picture. The subject matter will decide whether other pictures
will be similarly treated in the future. The mere application of a tone
is not sufficient : a choice of the color resulting from the treatment is
most important and vital for depicting the proper mood.

A toned photographic image is quite distinct from a tint, in that a
toned image consists of a color image embedded in a layer of colorless
gelatin, so that while the highlights are clear, the shadows are colored.
A tone may be applied chemically by the use of an inorganic metallic
salt or by the use of a dye. It is, of course, most important that the
toned photographic image be as transparent as possible for proper and
adequate projection. In this respect some samples of toned film that
appear fully toned upon hand examination produce a practically
colorless effect upon projection. It is important, therefore, when
judging a particular tone to view it upon a projection screen.

A toning machine had to be designed and built for the work, using
the general idea of a regular developing machine, rearranging the
tanks, however, so as to be suitable for the process. The tanks were
constructed of Allegheny steel and were set up in a lighted room, as a
dark room was not necessary for the operation. For that reason the
prints were not toned immediately after they were developed; they
were dried first, and then put through the toning machine, air squee-
gees being provided throughout the machine to prevent an excess
carry-over of water, chemical, and dye. The machine operates at a
rate of 90 to 100 feet per minute, depending upon the length of time
required for the toning operation. The toning solution is a chemical
one made up with uranium nitrate as the chief constituent. The
formula used was that contained in the 1927 edition of "Tinting and
Toning," published by the Eastman Kodak Company:

July, 1937] TONING POSITIVE FILM 67

Uranium Toning Formula — T9

Uranium Nitrate IG'A ounces

Potassium Oxalate lOVa ounces

Potassium Ferricyanide 6x/2 ounces

Ammonium Alum 2*/2 pounds

Hydrochloric Acid (10%) 1 quart

Water to make 50 gallons

The chemicals were mixed in the order given in the formula. The
temperature of the toning bath was approximately 70°F. The time
of toning was a variable, depending upon the depth of the tone de-
sired, varying from 1 J/2 to S'/a minutes. It is important to remember
that the effect of toning is to produce an intensification of the silver
image and that the intensification increases with the time of toning.
That means, of course, that the nature, or depth of the tone, changes
also.

The reaction of the toning bath is to replace the silver image in the
positive film by uranium ferrocyanide. The film is placed in a single
solution consisting of the metallic ferricyanide dissolved in a suitable
solvent, such as the alkaline salt of oxalic acid in the presence of a
mineral acid and certain other salts. The silver image is thereby
partly converted to a mixture of silver ferrocyanide and the corre-
sponding uranium ferrocyanide, thus producing a toned image. Fol-
lowing the toning operation it was necessary to wash the film com-
pletely so that all effects of the solution that are undesirable are re-
moved. Highlights should be clear and the time of washing should
be such as to render them clear. However, too long washing is det-
rimental, in that some of the color will wash out, due to the fact that
the uranium tone is soluble in water that is at all inclined to be alka-
line. Normally a ten-minute wash is sufficient.

The bath was made up in quantities of approximately 250 gallons,
and as the film passed through it the solution was maintained at the
desired strength by boosting at the rate of approximately two quarts
of fresh, five times normal strength toning bath for every 2000 feet of
positive film passed through it.

The picture The Good Earth was approximately 12,000 feet long,
consisting of 14 reels. There have been made from this negative ap-
proximately 500 release prints, and all the prints have been toned.

From the standpoint of sound, there is little to report other than the
fact that the sound department advised that all tests made by them
pertaining to the effect of toning the sound-track showed no detri-
mental effects upon the quality of the sound.

A TRANSMISSION-MEASURING SYSTEM UTILIZING A
GRAPHIC RECORDING METER*

W. W. LINDSAY, JR.**

Summary. — The design of a transmission-measuring system utilizing an Esterline
Angus recording meter is described. A circuit was developed requiring a special
triode exhibiting a logarithmic relation between change of grid bias and plate current.
The audio oscillator is a commercial type to which has been added a synchronous
motor drive geared to the frequency dial. For the amplifier -rectifier, required to oper-
ate the 5-ma. recording meter, use is made of a push-pull class A amplifier terminated
by a full-wave, approximately square-law tube rectifier, the d-c. output of the latter
being connected to the recording meter.

The paper concludes with a discussion of the various applications to which the sys-
tem may be put.

The need for a graphic record of transmission measurements has
been recognized for many years, particularly in connection with the
study of acoustical systems and other characteristics that play im-
portant parts in the development, testing, and maintenance of electri-
cal and acoustical apparatus.

The technical literature describes numerous systems developed for
this purpose, and many ingenious methods have been published,
ranging from a simple, hand-operated stylus to elaborate photo-
graphic registration. Logarithmic amplitude scales are most desir-
able, and it will be well to mention briefly some of the more funda-
mental methods used to obtain them. Ballantine used exponential
tetrodes.1'8 Best describes a direct-current instrument with special
pole-pieces.2 Wente, Bedell, and Swartzel use an amplifier and rec-
tifier, the gain being controlled by motor-driven potentiometers grad-
uated in logarithmic steps, the gain settings of which are recorded.3
European methods differ from ours: Payne and Storey utilize the
positive grid region of certain triodes.4 Thilo and Bidlingmaier use
the non-linear characteristic of copper-oxide rectifiers with tempera-
ture control.6 Peachey also uses the copper-oxide rectifier, but with-
out temperature control.6 Meyer provides a liquid potentiometer of

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.
** General Service Studies, Inc., Hollywood, Calif.

68

A TRANSMISSION-MEASURING SYSTEM

09

exponential shape.7 More recently, several modifications of the origi-
nal Ballantine method have been described.9' 10>u

A study of the various systems will indicate that a simple device
that will provide a logarithmic amplitude scale is not at hand without
resorting to a special tube and circuit, as described later.

In designing our present equipment, the fundamental requirements
we attempted to meet are as follows:

(1) The equipment must be stable, rugged, simple in operation,
and the recording portion must be portable and a-c. operated.

(2) The response must be independent of frequency from 35 to

FIG. 1. Experimental linear decibel scale amplifier.

10,000 cps., ±0.2 db., and effects of line-voltage change should re-
main within these limits.

(3) Effects of turn-over, wave-form errors, and stray magnetic
fields at power supply frequencies must be reduced to a minimum.

(4) A logarithmic amplitude scale that may be calibrated in deci-
bels, and logarithmic change of oscillator output frequency are de-
sirable.

(5) Accurate marking of the completed record should be made in
terms of the oscillator frequency dial calibration.

The first three requirements have been met in a satisfactory manner,
the fourth not at all, the fifth partially.

Experiments with most of the generally known circuits, as well as
several of our own, led us to believe it difficult to obtain a strictly
linear decibel scale and at the same time provide the required degree

70

W. W. LINDSAY, JR.

[J. S. M. P. E.

of stability, simplicity of operation, and freedom from line-voltage
changes or tube replacements.

The writer has developed a simple circuit (Fig. 1) which requires,
however, that the tube manufacturers supply a special triode in which
the plate current and grid bias follow the relation shown in Fig. 2,
which is a strictly logarithmic relation between grid bias change and
plate current. The usual variable-/* tubes do not follow this charac-
teristic accurately, or over a sufficient range to be of much value. In
Fig. 1, a class A push-pull amplifier terminates in a full- wave rectifier

MIUIAMPCRCS It>
K>dt>

Negative Bias Voltage Ratio

J L

J L

FIG. 2.

Negative bias voltage ratio (Curves 1 and 2 show charac-
teristics of 6D6 tube with different plate voltages) .

made almost perfectly linear by reason of a large value of load resis-
tance. The negative bias voltage produced as a result of signal rec-
tification is applied to the grid of the logarithmic triode. A milli-
ammeter in the plate circuit, and the recording meter with a variable
shunt resistance in the cathode circuit, permit proper adjustment by
means of the bias resistance, for full-scale deflection with reference
signal input. Linear input signal increments will result in a logarith-
mic reduction of plate current, obviously providing a linear decibel
scale. The range in decibels is limited by the ability of the class A
amplifier to supply signal voltage to the rectifier without overloading,
and by the tube parameters chosen in designing the special tube. A

July, 1937]

A TRANSMISSION- MEASURING SYSTEM

71

range of thirty to forty decibels should be possible. An advantage
possessed by this circuit arrangement is that excessive input signal
will not damage the recording meter, since the plate current is re-
duced to zero.

Space limitations and lack of a suitable commercially available con-
denser prevented adopting a logarithmic frequency change with re-
spect to time.1'8 A mechanical cam arrangement is the most simple

FIG. 3. Records obtained with the recording meter.

solution of the problem, particularly if a variable condenser is used
having a true "law" plate shape, such as a straight-line frequency
type.6

We found that the simple method of engaging the oscillator dial-
drive pinion at the beginning of the record is entirely satisfactory for
use as a frequency fiducial in applying the transparent chart to the
graphic record. This chart is marked in decibels and with frequencies
corresponding to the oscillator dial calibration. (Fig. 3, showing also

72 W. W. LINDSAY, JR. [J. S. M. p. E.

the overall frequency response of the equipment as well as the
effect of line voltage variation.)

Theoretical requirements have been so well covered in the bibliog-
raphy, that the remainder of this paper will be devoted to the prac-
tical problems of mechanical and electrical nature encountered during
construction of the apparatus.

A commercial audio oscillator (Fig. 4) has been provided with a syn-
chronous motor drive, connected to the frequency dial by means of a
set of gears. A small, hand-operated lever permits engaging the gears
so that the dial will begin rotating at the desired moment. The
number of gears is so chosen that the graphic record starts at the
high-frequency end of the scale. This is necessary with a left-hand

FIG. 4. Audio oscillator, with synchronous motor.

zero recording meter, otherwise the lower frequencies would appear
upon the right, instead of upon the left-hand, side of the chart, as con-
vention dictates. An additional pinion provides rotation in the op-
posite direction when making "toe" frequency negatives. The speed
of the motor and the gear ratios have been chosen to cover the fre-
quency range in sixty seconds.

A study of the circuit diagram (Fig. 5) will assist in following the
description of details used to attain the desired results.

The electrical circuits of the oscillator have been changed to provide,
in conjunction with an external booster amplifier, constant output
into 500 ohms, measured with a thermocouple instrument. The
changes consist in removing a low-pass filter and adding a suitable
output transformer and series capacity of the correct size to provide
low-frequency equalization, as well as a series resistance which hap-

July, 1937]

A TRANSMISSION-MEASURING SYSTEM

73

pens to affect both low and high frequencies, in the right amount.
The booster amplifier is normal, except that the input and output
transformers have been changed to more recent designs. The result-
ing output over the frequency range specified is well within the limits
set.

Having achieved a satisfactory oscillator-amplifier system, it re-
mained to work out an amplifier-rectifier arrangement that would
satisfactorily operate the five-milliampere recording meter. The

MODIFIED G.R.6I3-B AUDIO OSCILLATOR.
Ci C2

iH

FIG. 5. Circuit diagram of the system.

design chosen makes use of a push-pull class A amplifier, terminating
with a full-wave, approximately square-law12 tube rectifier, the d-c.
output of the rectifier being connected to the recording meter. This
provides an amplitude scale that is not linear in decibels, but is satis-
factory from a stability standpoint.

All the tube heaters are in series, and together with a small addi-
tional resistance, are connected directly to the 110- volt supply. The
B voltage required for the amplifier tubes is obtained from a voltage-
doubling circuit, without the use of a high- voltage power transformer.
The necessary filtering is obtained with capacity elements only. The
input circuit is of the high-impedance type, and may be connected

74

W. W. LINDSAY, JR.

[J. S. M. p. E.

FIG. 6. ( Upper) Amplifier-rectifier, with recording meter.
FIG. 7. (Lower) Same, with covers removed.

July, 1937] A TRANSMISSION-MEASURING SYSTEM 75

across a line having an impedance of 500 ohms in either direction
without serious bridging loss (0.2 db. at 35 cps.; less at higher fre-
quencies). The input circuit contains a series capacity and a shunt
resistance which serve to maintain the low-frequency response. The
input transformer feeds the signal to the two tube grids, and then
after amplification by the tubes, is transformer-coupled to the full-
wave rectifier. It so happened that this combination showed a
slightly rising characteristic up to 12,000 cps. The addition of a
small shunt capacity across the primary of the output transformer
provides uniform response from 35 to 12,000 cps.

Cathode resistor biasing was found to provide the required compen-
sation for line- voltage fluctuations. A +10-db. signal at the input
produces full-scale deflection of the meter. (Zero level equals six
milliwatts in 500 ohms.)

The full- wave rectifier is provided with a small adjustable resistance,
which is set for the initial calibration and may be reset at a later date
if necessary. In certain acoustic measurements, a large capacity
across the meter acts as an integrating device, and serves to smooth
out certain irregularities in the response curve, which are not of par-
ticular interest. Care must be used, however, in choosing its value,
since, if too large, it will give a false impression of flatness, and, also,
it shifts downward the peaks and valleys in the frequency response
curve. The value that we have found useful varies between 500 and
2000 /if across a 570-ohm meter movement. With this capacity in
the circuit, warble of the oscillator frequency is generally not used.

This completes the details of the oscillator-amplifier and amplifier-
rectifier recording meter combination. Fig. 6 shows the amplifier-
rectifier in its case, with the recording meter beside it. Fig. 7 shows
the same equipment with covers removed.

Applications to which the equipment has been put are as follows:

(1) Gain runs of all kinds, including amplifiers, microphones, loud
speakers, light-valves, frequency films, and records, etc.

(2} A recording microdensitometer has been achieved by using a
modulated light-source, moving the sound-track past a scanning aper-
ture at a slow, but uniform rate, and recording the amplified varia-
tions due to density changes.

(5) As a recording volume indicator, the instrument has been use-
ful in studying recording and re-recording signal amplitudes.

(4) The recording meter alone has been used for making direct
current or voltage records of various transient phenomena.

76 W. W. LINDSAY, JR.

Other applications are too numerous to mention, and depend chiefly
upon the problems at hand and the need for graphic record. The
time saved is quite appreciable, and permits giving greater attention
to other problems. The apparatus has been performing satisfac-
torily since July, 1936.

In conclusion, the author wishes to thank Mr. D. C. Hickson, Vice-
President, and Mr. J. R. Whitney, Sound Director, of General Service
Studios, Inc., for their cooperation in making this development pos-
sible; and also to acknowledge gratefully the many helpful sugges-
tions of his co-workers, Mr. J. G. Matthews and Mr. C. M. Ralph.

REFERENCES

1 BALLANTINE, S.: "Variable-mu Tetrodes in Logarithmic Recording,"
Electronics (Jan., 1931), No. 1, p. 472.

2 BEST, F. H. : "A Recording Transmission Measuring System for Tele-
phone Circuit Testing," Bell Sys. Tech. J. (Jan., 1933), No. 1, p. 22.

3 WENTE, E. C., BEPDELL, E. H., AND SWARTZEL, K. D., JR.: "A High-
Speed Level Recorder for Acoustic Measurements," J. Acous. Soc. Amer. (Jan.,
1935), No. 1, p. 121.

4 PAYNE, E. L., AND STOREY, J. G.: "A Portable Program Meter," The
Wireless Eng. & Exp. Wireless (Nov., 1935), No. 11, p. 588.

5 THILO, H. G., AND BIDLINGMAIER, M. : "The Tone Meter," E. N. T. (May,
1936), No. 5, p. 176.

6 PEACHEY, F. A.: "Automatic Line-Level Recording Apparatus," Wireless
Eng. (Sept., 1936), No. 9, p. 462.

7 MEYER, E.: "Reverberation and Absorption of Sound," J. Acous. Soc.
Amer. (Jan., 1937), No. 1, p. 155.

8 BALLANTINE, S. : "A Logarithmic Recorder for Frequency Response Mea-
surements at Audio Frequencies," /. Acous. Soc. Amer. (July, 1933), No. 7, p. 10.

9 WHEELER, H. A., AND WHITMAN, V. E. : "Acoustic Testing of High-Fidelity
Receivers," Proc. I. R. E. (June, 1935), No. 6, p. 610.

10 HUNT, F. V.: "A Vacuum-Tube Voltmeter with Logarithmic Response,"
Rev. Sci. Instr. (Dec., 1933), No. 12, p. 672.

11 TAYLOR, J. P.: "A D-C. Amplifier for Logarithmic Recording," Electronics
(March, 1937), p. 24.

11 WOLFF, I. : "Alternating- Current Measuring Instruments as Discrimina-
tors Against Harmonics," Proc. I. R. E. (April, 1931), No. 4, p. 647.

DENHAM STUDIOS OF LONDON FILM PRODUCTIONS

LIMITED*

L. C. FERMAUD**

Summary. — The studios occupy 28 acres of a 165-acre estate in Buckinghamshire
about 17 miles from the center of London. Fine gardens stretching to the edge of
dense woodland provide a natural setting that can be adapted easily for exterior pho-
tography. There are seven stages, totalling 120,000 square-feet of floor area. Two
stages are 250 by 120 by 45 feet (high) ; two are 125 by 120 by 45; and three are 120
by 80 by 35. Details of the foundation and wall construction are given. The main
reviewing theater is designed for reviews and for scoring; for the latter the reverbera-
tion period can be adjusted to 0.8 second and for the former, 1.5 seconds.

A description is included of the various shops that service the studios, not only
for set construction but also for equipment. The metal shop, for example, has turned
out more than 700 lamps for set lighting, two optical printers, a projection printer, a
stop-motion machine, and a rear projector.

In the sound stages, only the dubbing channel is of the permanent type. A brief
description is given of the portable sound channels, the camera department, and the
processing laboratories. Two automatic developing machines, capable of developing
480 and 1000 feet per hour, are available for film processing. Automatic mixing
equipment is used for preparation of solutions.

The electrical power plant is described and details are included on fire protection,
water supply, and sewage disposal.

It is important that a British studio be situated in close proximity
to good natural settings so that production hold-ups may be reduced
to a minimum by the use of alternative exterior and interior schedules
for fine or wet weather. London Film Productions' studios are hap-
pily situated in this respect in that the estate, though only some seven-
teen miles from the center of London, is in the heart of Buckingham-
shire's reputedly fine scenery.

The estate itself is 165 acres in area, of which the studio occupies
28 acres. The River Colne winds through the estate for ll/^ miles,
and widens out into a lake by the lawns of the Old House, formerly
the residence on the Denham Estate. There are fine gardens stretch-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
April 19, 1937.

** London Film Productions, Ltd., Denham, Middlesex, England.

77

78

L. C. FERMAUD

[J. S. M. P. E.

ing to the edge of dense woodland possessing a surprising variety of
trees, while the upper reaches of the river run through typical English
meadowland.

It is there that many permanent sets have been constructed in a
setting that can be easily adapted for exteriors of almost every kind.
The site is naturally insulated against sound, for the only chance of
noise on one side — a country road — is effectively screened by trees in
most parts, while on the other the country is entirely devoid of build-
ing development. The possibility of the spoiling of the sky-line is
remote, for large areas of the surrounding country and part of the

FIG. 1. General layout of the studios.

estate are included in a town-planned green belt upon which building
can not take place for at least twenty years.

The value of such locations, literally at the back door of the studio,
can not be gainsaid. Production units remain under executive super-
vision, and also have the advantage of the studio power supply, stores,
accommodation, and catering arrangements.

Such was the setting chosen by Mr. Korda for the construction of
a studio at least as modern, it is hoped, as any in the world. It was
commenced with the initial advantage that it was to be built as one
complete whole, and all possibilities of future development for many
years to come laid out in the original plans.

The tremendous amount of thought arid knowledge put by Mr.
Jack Okey into the scheme can only now be fully appreciated, for the
studio was built at a time when contractors and specialists in this

July, 1937] DENHAM STUDIOS OF LONDON 79

country had little experience with plants of such size, with their
trains of pitfalls. All the pitfalls had to be watched for and avoided,
and a scheme evolved that was to house a complete community ca-
pable of making sound and color-films upon a large scale. Everything
possible was to be produced on the premises, with a minimum of calls
upon outside resources, from power supply to the processing of the
exposed film.

Fig. 1 shows the general layout of the studio. The main entrance
and gatehouse are at the top left-hand corner, and the garage just
below. There are three entrances to the front block of buildings,

FIG. 2. Front view of stages.

south, central, and north. The administration offices are grouped
near the south entrance, together with the sound department, main
review, and scoring theater. The executive offices are situated on the
first floor overlooking the main entrance and the surrounding coun-
tryside. The central entrance is, in effect, a private entrance giving
access to an individual two-story block of offices for the use of renting
companies.

Dressing rooms, make-up, wardrobe departments, and casting
offices are grouped near the north entrance, where crowds are checked
in and paid off. Beyond is the studio restaurant. The whole of this
front block is interconnected with corridors and glass-covered ways
that feed into a main transverse corridor connecting the stages — the
hub of all film studios. Covered ways are a very necessary feature.
Apart from access to the shops, there is little need for anyone to go

80 L. C. FERMAUD [J. S. M. P. E.

into the open air, where costumes may be damaged by rain or one may
catch cold by the sudden changes of temperature in the winter time.

At the base of stages 4, 5, and 7 are three two-story annexes,
housing, respectively, the special-effects department, art department,
and the still and camera departments.

The power station will be seen placed centrally, immediately below
the stages with the two stage air-conditioning fan chambers, and the
boiler house adjoining. This position for the power station was
chosen in order to reduce to a minimum the length of the bus-bars to
the stages, with the resultant saving in cost and minimizing of the

FIG. 3. Rear view of large stages.

voltage drop. The workshops are housed in three buildings to the
south of the stages, the various departments being arranged as far as
possible in the order of the procedure of work.

Owing to the large area that a number of sound stages must cover,
even when grouped as closely as practicable, and the consequent long
distances to be traversed, it was considered most satisfactory to ar-
range the shops together in one group for easy intercommunication,
and to feed their output to the stages in low-loading lorries.

With the exception of the road leading down from the main en-
trance, which is thirty feet wide, all roads are twenty-five feet wide
with five-foot grass verges on each side, giving a standard distance
between buildings of thirty-five feet. Though it has proved difficult

July, 1937] DENHAM STUDIOS OF LONDON 81

to persuade the grass to keep on growing, the green verges add greatly
to the impression of airiness about the studio. Fig. 2 shows the front
elevation from the dressing room end, and Fig. 3 the rear of the large
stages with their annexes and air-conditioning extract turrets.

All buildings are steel framed. A total of 4500 tons was used.
There are over 700 tons of steel in each of the three large stage build-
ings. Apart from the shops, where the walls are covered with asbes-
tos sheeting, and stages 1, 2, and 3, where they are of brick, walls are
of 4-inch reinforced concrete. The low-pitched roofs of the front
block, which are concealed by parapet walls, are of roofing felt laid
upon close boarding on wood purlins. The remainder of the 25-

FIG. 4. General view of studios from the air.

degree pitched roofs of the stages, power station, shops, etc., are of
green-colored asbestos cement, "Watford" tiles. These green roofs,
which blend with the natural green of the countryside, were decided
upon after cooperation with the local town-planning authorities, who
were as anxious as the Company that the studio should not spoil the
amenities of the district by striking a contrasting note.

The broad, square corrugations of the gray asbestos cement sheets
used on the shops is a great improvement on the more usual 3-inch
corrugated material. Moreover, it is not so liable to breakage. If
breakage does occur, individual sheets can be quickly and inexpen-
sively replaced without disturbing the rest of the wall.

It was decided to build stages 1, 2, and 3 only after the major part
of the studio was completed. The stages were required urgently,

82

L. C. FERMAUD

[J. S. M. P. E.

and are consequently made of brick, for brick is the British work-
men's favorite type of construction, and at which he is quickest. The
tie-beams between the stanchions were laid upon their sides, and the
41/2-mch brick panels built upon the webs for stability. The exposed
flanges were afterward wire-lathed and the exterior rendered in
cement.

The entrance halls, principal offices, and stars' dressing rooms are
finished in plaster. The remainder of the offices and dressing rooms

FIG. 5. Sound stages under construction.

are papered on wallboard on stud partitions. This type of construc-
tion, apart from being cheap, possesses the advantage that partitions
may be removed, or new doors cut, very easily and without the need
for complete redecoration.

Fig. 4 is a general view of the studio from the air — the workshops
upon the right, the semicircular end of the main review and scoring
theater just inside the main entrance, and the laboratories, where the
film is processed, on the extreme left.

Fig. 5 shows the sound stages during the course of construction.
Each of the roof trusses, which are composed mainly of double chan-

July, 1937]

DENHAM STUDIOS OF LONDON

83

nels, weighs twelve tons, and is designed to carry a load of two hun-
dred pounds per foot run of truss. Interlocking steel shuttering was
used for the concrete work, the walls being raised uniformly by pour-
ing a four-foot ring of concrete every day, except, of course, when
heavy frost caused a hold-up.

The framing to the stage walls is seen in Fig. 6. The double
stanchions at the lower part of the wall were required in order to keep
air-conditioning input ducts within the thickness of the wall without
encroaching upon the floor space. These ducts branch off the main
duct, the trench for which is at the base of the wall.

FIG. 6. Interior of large stage.

The seven stages total 120,000 square-feet of floor area. There are
two each, 250 X 120 X 45 feet high, two 125 X 120 X 45 feet high,
and three 120 X 80 X 35 feet high. The two 125 X 120-foot stages
are in reality one stage identical to the two large stages, but with a
sound-proof dividing partition across the center.

The floors of all stages are composed of 1-inch G & T boarding,
secret-nailed to 1-inch close boarding. Water-proof paper was laid
between the boardings to prevent squeaking. There is an ample num-
ber of electricians' runways in the roof trusses to facilitate lighting.
The stages are also equipped with tracks and chain tackle. All doors,
including those of the shops, are of standard size, 20 feet high by 16
feet wide, so that anything that can be got out of the shops can also
enter the stages, and vice versa.

84 L. C. FERMAUD [J. S. M. p.

Particular attention was given to the design of the sound-proofing
and acoustic treatment, particularly in the case of the bigger stages,
where it was thought that the large area of the comparatively thin
walls would tend to transmit sound by resonance. It was conse-
quently thought necessary to form an inner shell for both walls and
roof with a dead air space between it and the structure, the shell to be
isolated from the main structure as far as possible so as to prevent the
passage of sound by vibration.

The treatment decided upon for the walls consists of a 6 X 2-inch
wood frame spaced about iy2 feet from the outer wall. This is tied
to steel channels fixed to the inner face of the main stanchions by
bolts insulated from the steel frame by cork sleeves and washers.
Two-inch sheets of woodrock, a material consisting of wood shavings
cemented together, were nailed to the wood frame, then 1/2-inch
plaster board, and finally rock-wool blankets. The inner shell of the
roof is of similar construction. It is secured to a second row of pur-
lins hung from the main purlins by steel straps and insulated from
them by cork seatings. The actual asbestos roof was laid directly
upon two layers of woodrock. The sliding doors are all double, the
outer one hung from the steel frame, and the inner from the sound-
proof shell. They are structurally separate, and are 4 inches thick,
composed of two outer layers of 1-inch G & T boarding, the inter-
vening space being composed of celotex sheets. Splayed felt and
rubber buffers prevent the passage of sound at the edges.

The dividing partition between stages 6 and 7 presented a special
problem, particularly since doors were required between the two
stages. A system similar to that employed for the external walls
was followed. Two wood-framed partitions were secured by cork-
insulated bolts on each side of a supporting steel frame upon separate
foundations. The doors in this case were hinged, to provide a better
seal, and are entirely independent of each other.

The sound-proofing of the stages proved very efficient. As a test,
the noise of an aeroplane flying 500 feet directly overhead was not
sufficient to have prevented shooting. Production can also be con-
tinued in stages 6 or 7 while sets are being erected in the other, the
dividing partition satisfactorily baffling the sound.

Another acoustic problem, the only one of its kind in this country,
is the main review theater. In order to -avoid a duplication of thea-
ters, it was necessary that it should not only have a suitable rever-
beration period, and good appearance for important reviews, but

July, 1937] DENHAM STUDIOS OF LONDON 85

should also possess a variable reverberation range for scoring and
dubbing. The range required was from 0.8 second for scoring and
dubbing to 1.5 seconds for review, which is obtained by a number of
reversible hinged panels upon the side walls. These panels are 4
feet wide X 28 high, and are constructed of wood upon a steel frame
tied to a tubular steel rod at the hinged side to prevent whipping.
One side is covered with 3/8-inch plywood painted to conform to the
general color scheme, and the other is padded with rock-wool. In
spite of their weight, the lightness of their bearings renders it a simple
matter to reverse them. Large sliding doors can be pulled across the
front of the screen to form a sound-reflecting background for an
orchestra.

The two shop buildings running parallel to the stages are 272 feet
long (the same length as the stages plus their annexes) by 80 feet
wide. They house, in one, the modellers, plaster, paint and pattern
shops, and the grips storage; and, in the other, the electrical equip-
ment and property storage, and the papier mache and drapery shops.
The third shop building contains the general stores, carpenters'
shop, mill, timber racks, metal shop, foundry, and blacksmith.
These buildings are specially well lighted by side windows and broad
roof lights. The interiors are distempered white, the doors, offices,
etc., being painted a pale gray.

The carpenters' shop is 192 X 120 feet in area, which provides
ample space for the laying out and constructing sets under cover.
The mill adjoining contains all the heavy machinery. Timber is
drawn in bulk from the racks, which open directly into the mill, for
cutting on the self-feed circular saw. These two shops are fully
equipped with the most up-to-date machinery available, including
tenoning and mortising machines, spindles, band-saws that cut to any
radius, a lathe, self-feed planing machines that will take material up
to 26 inches wide, and a jointing machine. Two portable circular
saws are also available for bench use.

The metal shop is, without question, the finest of its kind in Europe.
With the assistance of the pattern shop in preparing the wood pat-
terns for the moulds, there is practically nothing that it can not pro-
duce. Apart from normal production work and equipment main-
tenance, more than 700 lamps for set lighting, two optical printers, a
projection printer, stop-motion machine, and a rear projector, have
been turned out, practically in their entirety.

The shop is equipped with power hammers, hacksaws, and planing

86 L. C. FERMAUD

machines, nine lathes from 4x/2 to 9 inches, a shaper, a radial drilling
machine, tool grinders and cutter grinders, a fully universal milling
machine with attachments for gear cutting, an electric spot welder,
and two oxyacetyline welding plants. There are also bending ma-
chines, guillotines, rollers, and presses for the sheet-metal workers.
Opening off one side of this shop are the foundry and blacksmith's
shop equipped with three foundry furnaces for 60 to 120-pound pots,
and a forge. Camera repairs are carried out in a small specially
equipped shop in one corner of the metal shop proper.

Owing to the relatively high cost of timber, some 75 per cent
greater than in Hollywood, a considerably greater amount of plaster
work is done in the plaster shop than is done in the American studios.
Twenty- or thirty-foot columns that might otherwise be of wood are
molded more economically in plaster. The shop is 80 feet square.
During production peaks, more than 200 men have used 42 tons of
plaster in a week. Considerable quantities of plaster work are
stored in a separate building outside the doors of the plaster shop.

The next shop in this block is the painters,' which includes a
mechanically ventilated spray room, a sign writers' room, and a
finishing shop. Then there is the pattern shop, 64 X 80 feet,
equipped with its own machinery, and the grips, which includes the
camera equipment store, and special-effects model store.

Each of the two floors of the property store are 144 X 80 feet in
area, and include a separate store equipped with cupboards, racks,
unpacking tables, etc., for small properties. Most properties that are
not normally kept in the studio can be obtained in London, although
not from one particular source. Many large shops specialize in a
single type or period of furniture, such as Queen Anne, Louis XV and
XVI, or modern sycamore. Consequently, much depends upon the
experience of the property buyers in knowing where to look for their
material.

The electrical repair shop and store look after all electrical floor
equipment, as distinct from electrical supply. It possesses nearly
1000 lamps from 1000-mm., high-intensity arcs to the smallest photo-
floods, seven portable generators for location work with capacities up
to 1000 amperes, and more than 30,000 feet of cable. Mention must
also be made of the six electrical wind machines, two lightning ma-
chines, and the rain effects. Most of this equipment was made in the
studio shops.

The drapery shop follows normal procedure. It contains the usual

July, 1937]

DENHAM STUDIOS OF LONDON

87

racks, benches, and sewing machines, and .facilities for stencilling.
A well on one side of the shop enables large quantities of drapes to be
stored, up to a length of about 30 feet.

Fig. 7 shows the internal planning of the front block in more detail.
There are 56 dressing rooms, 16 for stars and 40 for small-part
players. Each star's room has a bathroom adjoining, and four of
them have private sitting rooms. With the exception of the chairs,
all the furniture was designed and made on the premises. Dressing
table and table tops are covered with sheet aluminum, which looks
attractive, does not crack, can be easily cleaned, and is fire proof .
The two "crowd rooms," each capable of accommodating 500 extras
are equipped with steel lockers, and showers in a separate room.

The wardrobe department, on the opposite side of the corridor
from the make-up department, covers an area of 102 X 57 feet, and

FIG. 7. Plan of the front block.

contains the wardrobe room proper, a large workroom and store-
room, two fitting rooms for men and women, costume designers'
rooms, and offices. Ten thousand costumes have been handled with
ease.

The sound installation comprises equipment to cover the needs of
the seven stages, two review theaters, and the large combined review,
scoring, and dubbing theater. To assure maximum flexibility, only
the dubbing channel is of the permanent type. Permanent wiring
between the stages and "Bay X," a central control panel enables
portable channels to be used from recording rooms to serve any two
stages, other stages being served by recording trucks. By this means,
the problem of location work is simplified, as a minimum of time is
required to get a unit ready for changing over. Since it is imperative
to construct cover sets owing to climatic conditions, flexibility is of
paramount importance in equipping an English studio.

88 L. C. FERMAUD [J. S. M. P.

For foreign location work, the type F channel still remains tl
most satisfactory, since in its compact units it can be carried ovt
ground that would be impassable to a loaded truck. The FB chan-
nel, though not so compact, can not be bettered from the point
view of reliability. It is a testimonial to the consistency and excel-
lence of the product that for us the latter is the accepted standard
quality. The new QB channel at first presented some difficulty
owing to its extended frequency range, and coupling with that the
use of the new 630 microphone, it was found necessary to review mi-
crophone technic to meet the new conditions. Disk recording ge
is available for all stages. There are also two type F, two FB, and
three QB channels.

Power supply is obtained from an independent power room in the
basement below the sound department, where the studio d-c. supply
is converted into the various a-c. and d-c. voltages required by the
sound equipment. There is also a film processing room where a check
is kept upon the behavior of the developing and printing laboratories,
and the test-room where everything comes to pieces sooner or later.

The camera department possesses its own offices, darkrooms, test-
rooms, and storerooms. To avoid the risk of fire, all camera equip-
ment is kept in fire-resistant steel lockers, and only the days' supply
of negative film is brought from the vaults to the test-room. The
equipment includes eighteen cameras, including eight super-Parvo
Debries, four N. C. model Mitchells, and three Newman Sinclair,
four Fearless Panorama Velocilators, an electric velocilator, and a
camera crane. Eleven units have been serviced satisfactorily at one
time.

The still department is equipped for all types of work — publicity,
fashion, portraits, and color photography. It is at present capable
of producing 1000 prints a day, but room has been allowed for expan-
sion. There is one Kodak auto-focus enlarger, two miniature en-
largers, two Kodak printing machines, and the usual print develop-
ing and washing facilities. All development is carried out in rooms
at standard temperature by tank at fixed time and temperature. The
negative drying room is also of standard temperature, with a con-
stantly circulating current of air passing through it. Each negative
dries in 40 minutes in a controllable temperature, to prevent the
emulsions from becoming brittle; 750 10 X 8-inch negatives can be
dried per day. A portrait studio with two dressing rooms is incor-
porated in the department, in which facilities are available to enable

July, 1937] DENHAM STUDIOS OF LONDON 89

sets to be introduced so that stills may be in -keeping with stage pro-
ductions.

Trick work, up to recently, has not been used so widely in England
as in America. In view of the type of their productions, however, the
Company has gone to considerable pains to provide itself with a
thoroughly equipped special-effects department. It is self-contained,
with its own developing, printing, cutting, camera, and darkrooms,
projection theater and insert room. A large concrete tank has also
been constructed in the grounds for trick work. It is 150 X 120 feet
in size with a 40-ft. high steel framed backing along one side, and a
30,000-gallon dump tank with a 30-ft. head of water nearby.

As has been stated, much of the special-effects equipment has been
designed and made in the studio. This has been necessary since ma-
chines with the necessary range of operations could not be obtained.
The major items of equipment include two rear-projection machines
with Bell & Howell camera movements, which give perfect registra-
tion and assure a steady picture on the screen. These machines are
equipped with Brenkert high-intensity arc lamps. There are also a
stereopticon projection machine with which a slide can be held upon
the screen for as long as iy2 hours, without danger of damage to the
slide from heat, and an ice-cooled fog machine capable of laying a fog
non-injurious to health.

In the optical printing room, are a projection printer and two op-
tical printers. The former has an adjustable screen with clips for
holding sheets of glass so that the operator can project pictures upon
the screen and take out any part of the picture being projected, and
then photograph with a Michell camera mounted on the other end of
the bed. The optical printers are equipped with standard Bell &
Howell camera movements.

There is also a contact printer which is used to make blue-prints
for the optical printer as well as rear projection prints. The light is
brought in contact with the film through a lens with a number of
ground glasses between the light and the lens in order to obtain an
even field of light. By the use of various glasses having darkened
centers, "hot-spots" on the projection screen can be eliminated.
This printer was designed because a contact print is sharper and
steadier than an optical print, and can be made at much lower cost.
There is also a standard Bell & Howell continuous printer for daily
rushes as well as for projection prints that are moving.

In the laboratory are two automatic developing machines, capable

90 L. C. FERMAUD [j. s. M. P. E.

of turning out between 480 and 1000 feet of film per hour. The time
of developing can be changed while working, without stopping the
machine. Each machine has its own refrigerating plant, heating
system, and pumps for circulating the solutions. The laboratory is
also equipped with an automatic mixing machine for mixing the
chemicals, and water filters and softeners.

The cutting department, with its 14 cutting rooms and film vaults,
is situated near the Old House. They are equipped with Moviolas
and the usual modern cutters' equipment. Most of these cutting
rooms were brick built stables, converted for the sake of economy.
The music department is nearby. It is an old cottage modernized,
and is away from the noise of the studio proper.

Many factors required careful consideration before a decision could
be made on the system of power supply. Steam turbines, Diesel
engines, and a supply from the public companies were all considered.
The steam plant was ruled out, due to the possibility that the dirt
arising from the coal boilers would affect the air-conditioning of the
stages. Supply from a public company would have been very con-
venient, but the cost of acquiring such a supply and converting it to
direct current made this course prohibitive. Apart from these rea-
sons, the Diesel-electric system was chosen because capital charges
were in its favor, and the possibility of "black-outs" due to interrup-
tion in the supply were at a minimum compared with other systems.

The plant consists of six Crossley- Premier oil engines, each directly
connected to a Mather & Platt three-wire static balanced generator,
each of 750-killowatt capacity, giving a total output of 4500 kilo-
watts. The power station was designed to take two further sets,
making a total of eight to allow for the increased demand when future
stages are constructed. The generators are designed to supply 230/-
250 volts across the outers of the three wires. Overload capacity is
25 per cent for two hours, obtained by supercharging the engines.

Fig. 8 shows four of these generator sets. They are mounted on
heavy concrete bases some seven feet deep, which in turn rest upon
the foundations. Between these two masses of concrete is a three-
inch mat of cork to eliminate vibration. The bus-bars and cables
are in the alleyways formed between the bases below the general floor
level.

On the control desk six sets of push-button panels control the gen-
erators. On the front of the desk are the field regulators and switches,
the regulators themselves being operated and mounted in the base-

July, 1937] DENHAM STUDIOS OF LONDON 91

ment below the control room. A Chadbufn electric telegraph en-
ables the control engineer to signal for any machine to be started or
stopped; in addition he has an excellent view of the engine room
through the window at the back of the desk.

Fig. 9 shows the switchboards at the sides of the control desk de-
voted to the smaller feeders. The main studio circuits are controlled
by hand-operated circuit-breakers in the basement, from which the
bus-bars run on the roofs of the ventilating ducts to the distribution

FIG. 8. Four of the six 750-kw. generators in the power plant.

panels at stage-floor level, and also to the catwalks from which the
overhead lights are controlled. The power for the workshops
is supplied by two motor-alternators of 220-kva. capacity at 400
volts. Fuel for the Diesel engines is stored in a 50-ton tank in the
open air, adjoining the power station. It is enclosed on all sides by a
concrete wall.

Starting air is stored in two cylinders at 250 Ibs. per square-inch,
and is normally supplied by a motor-driven compressor. Due to the
importance of reliability, the compressed-air storage capacity was
made sufficient to enable each engine to make six starts from cold, a

92

L. C. FERMAUD

|J. S. M. P. E.

total of forty-eight starts, before recharging is necessary. In the
event of the station's being put out of commission, and the charge
in the cylinders becoming lost, air can be compressed by a small inde-
pendent hand-started Diesel engine. An individual Ingersoll-Rand,
Mather & Platt, motor-driven service compressor, situated in the
power station, supplies compressed air to numerous points in the
stages, shops, etc.

•Bill

FIG. 9. Feeder circuit switchboard.

The water services presented a special problem. The service had
to cover not only the domestic and hot water supply for the offices
and dressing rooms, but the supply for the air-conditioning plant,
stage heating, and engine cooling. In view of the tremendous quan-
tity required, the cost of a supply from the local water company
mains would have proved exorbitant.

To obtain a supply for engine cooling was comparatively simple,
since the river passes within a hundred yards of the power station.
The water is pumped from it to tanks situated on the power station

July, 1937] DENHAM STUDIOS OF LONDON 93

roof. The remainder of the supply is obtained from an artesian well
bored to a depth of 320 feet. The water is pumped at the rate of
10,000 gallons an hour to a reinforced concrete water tower concealed
in the woods. From the tower, a network of mains runs to the various
parts of the studio, and to a number of local supply tanks.

The heating of the studio is divided into four systems operated
from three individual sources of supply. These are, briefly, air-con-
ditioning to the four larger stages; low-pressure hot water for the
three smaller stages and annexes; gas-hot-air radiators for the work-
shops; and low-pressure hot water again for the front block.

Owing to the considerable length of pipe runs that would otherwise
be required, it was considered necessary to install an independent oil-
fed boiler plant for the front block heating. The other boiler plant
adjoining the power station, and which can virtually take its supply
of heat under heavy load conditions from waste-heat boilers in the
power station, feeds the air-conditioning plant and the smaller stage
and annex heating.

The studio also possesses its own sewage disposal plant, which was
necessary owing to the absence of a public sewer in reasonable proxi-
mity to the studios. The sewage gravitates to collection tanks from
which it is pumped through a rising main to the disposal plant at the
far end of the estate.

The major part of the studio is protected from fire by a sprinkler
system. The whole of the workshops, stages, offices, etc., can be
covered by means of fire hose connected to a large number of stand-
pipes around the site.

Last, there is the estate department, which, apart from cultivat-
ing shrubs and flowers, and tropical plants in the seven glass-houses,
endeavors to keep the estate tidy in spite of the fact that a set always
is built exactly where they have just finished some planting.

The writer is indebted to Mr. Watkins of the sound department,
Mr. Denham, the engineer, Mr. Mann and Mr. Woods of the special-
effects and still departments, respectively, and to others of Mr.
Alexander Korda's organization for their assistance in supplying
the information concerning their departments and equipment.

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus are held, in which various manufacturers of equipment describe and demonstrate
their new products and developments. Some of this equipment is described in the
following pages; the remainder will be published in subsequent issues of the Journal.

THE SUPER SIMPLEX PEDESTAL*
J. FRANK, JR.**

During the nine years since the introduction of sound reproducing equipment,
the motion picture industry has witnessed the development of more heavily con-
structed devices, often of considerable weight, such as modern sound reproducers
with directly connected motors in front, heavy-duty arc lamps, more sturdily
designed projector mechanisms, and larger magazines. The weight of all this
apparatus is far in excess of that for which the earlier pedestals and stands support-
ing all these units were designed. More recently the introduction of the standard
2000-ft. release print has placed a further burden of weight upon motion picture
projection and sound reproducing equipment. To meet these demands, the
International Projector Corporation has placed upon the market a new supporting
pedestal.

The new Super Simplex pedestal is extremely symmetrical, harmonious in de-
sign, and provides an excellent balance for the heavy-duty equipment it must
support. It has also been designed to permit all the necessary quick adjustments
greatly desired and appreciated by projectionists.

Previous pedestals were designed for the old type silent projection equipment
using slide-over attachments for the projection of stereopticon slides. This made
the pedestal somewhat flimsy; but nevertheless it adequately supported the
equipment that was mounted upon it. Modern equipment mounted upon such a
pedestal is not properly balanced due to the location of the pivot point. Further-
more, the great weight of the equipment places a burden upon the old pedestals
that almost reaches the danger point. The new Super Simplex pedestal ade-
quately meets the requirements. The pivot point has been moved back under the
lamp house table, resulting in excellent balance, and requiring only the slightest
exertion to raise, lower, or horizontally adjust the entire apparatus, so that at an
instant's notice it may be accommodated to the screen position.

Two convenient adjustments are provided, one for tilting, and the other for

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received
April 1, 1937.

** International Projector Corp., New York, N. Y.

94

NEW MOTION PICTURE APPARATUS 95

lateral displacement. The former adjustment has a unique feature eliminating
the necessity for a long lead-screw. Three positions for the horizontal rod sus-
pension have been provided. This permits the use of a short lead-screw for tilting.
With the rod in the top position the pedestal is locked into position at the maxi-
mum angle of tilt by the control. Then the thumb-screw on the horizontal rod
is loosened and the rod easily removed. The lead-screw is then adjusted so that
the horizontal rod may be properly placed in the center position. The pedestal
may then be further tilted. By repeating this operation and placing the horizon-
tal rod in the lower position, angles of tilt from minus 3 to plus 33 may be easily

FIG. 1. Super Simplex pedestal and RCA
Photophone rotary stabilizer sound head (oper-
ating side).

accomplished. The lateral adjustment, accessible from either side of the pedestal,
permits a horizontal angle of approximately 3Vz degrees about the pivot point
located in the rear of the pedestal. Four knobs are turned to lock the pedestal in
its horizontal position. When the pedestal is installed and the adjustments finally
locked in place, the entire assembly is rigidly mounted, and the absence of vibra-
tion, due to the great weight of the whole unit, gives a steadiness to the entire
equipment heretofore unobtainable.

The pedestal is provided with a spacious internal compartment into which may
be brought all electrical connections, thus eliminating the network of wires and
cables distributed around the projector in an unsightly manner. Where it is not
convenient to bring up the conduits through the floor in the proper position, they
may be brought into the compartment through a plate especially provided in the

96 NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

non-operating side. If this is not necessary, this plate provides a suitable location
for a fuse-box, if desired.

Two flush twist-lock receptacles are located on the non-operating side, one a
three-pole for the change-over device, and the other a two-pole for the operating
motor. This allows for readily disconnecting either of these important circuits
without the necessity of breaking soldered joints, when the occasion arises for
making a quick change of equipment.

Two 3-way, 30-ampere switches, one on either side of the pedestal, are
mounted upon the pedestal for the operating motor circuit, so that the motor may

FIG. 2. Super Simplex pedestal and ERPI
heavy-duty Mirrophonic reproducer (operating
side).

be readily controlled from either side of the equipment. A further improvement
is provided through a number of double-pole standard outlet receptacles into
which may be plugged soldering iron, work light, threading lamp, or other auxil-
iary equipment. The arc lamp feed-motor also may be connected to one of these
to provide an instant means of disconnecting this unit when necessary.

A universal type spirit level forms part of the unit, so that the equipment may
be accurately levelled in the projection room when installation is made. The
base of the pedestal is provided with levelling bolts fitted into solid steel cupped
flanges, so that the stand may be levelled at all corners and still give excellent
rigidity regardless of the unevenness of the surface upon which it stands.

The lamp house support bracket is of entirely new and unique design. It is of
much more ample dimensions than any heretofore constructed, so that its length

July, 1937]

NEW MOTION PICTURE APPARATUS

97

adequately supports the much longer lamp house structure than was possible on
any pedestal previously designed. For the first time it is possible with this unit to
align accurately any type of standard lamp house regardless of slight errors that
may exist in manufacture, so that the positive carbon axis is in accurate alignment
through the optical system. The bracket may be tilted upward or downward at
either end, from side to side, and raised or lowered vertically as a complete unit.
This is accomplished by providing holes for the mounting screws twice as large as
the screws, permitting displacement in all directions. A screw at the rear posi-

FIG. 3. Diagram of pedestal, showing adjustments.

lively controls the vertical adjustment at the rear. Large washers and nuts per-
mit positive fastening of the screws in any desired positions in the large holes.
Absolute rigidity is obtained by tightening the four nuts involved.

When lamps of the low-intensity or high-intensity Suprex arc type are used, a
100-ampere, double-pole knife-switch is provided, mounted in a heavy cast-iron
switch-box attached to the pedestal. Where straight high-intensity arc equip-
ment is used a heavy switch-supporting bracket attached to and supported by the
rear lower pedestal section is furnished, and it is recommended that a heavy-duty,
200-ampere switch and switch-box such as the "Square D" be used. The heavy-
duty switch-supporting bracket is sold at a slight additional cost. Three holes

98

NEW MOTION PICTURE APPARATUS

with insulators are located in the rear of the pedestal through which the asbestos
wires for the arc lamp supply may be run.

A flat surface is located on the front operating corner of the pedestal, to which a
standard change-over may be attached.

Since the sound reproducers of various manufacturers are not standardized in
design, it is not possible with a pedestal of unit design to conform to all existing
projection port-hole constructions because the relative position of the mechanism
to the pivot point varies as much as 8 inches, depending upon the sound reproducer
employed. Spacers, therefore, are furnished in 1-, 2-, 3-, 4-, 6-, and 8-inch sizes to fit
between the lower and upper pedestal sections to fit the existing port -hole location.

For the same reason a number of different sound reproducer support-arms are
available. The proper support-arm for the sound reproducer to be installed is
furnished as part of the pedestal. With some types of sound reproducers it is
necessary, for angles greater than 20 degrees, to provide a special support-arm to
avoid interference between the pedestal front and the rear of the lower magazine.

The new Super Simplex pedestal will accommodate the Simplex sound projec-
tor, Type 5.4, in which case the lamp house bracket is eliminated. The 100-
ampere arc lamp switch is furnished for this equipment.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D. C.,
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

Academy of Motion Picture Arts and Sciences, Techni-
cal Bulletin

(March 31, 1937)

Specifications — Standard Electrical Characteristics for
Two-Way Reproducing Systems in Theaters (p. 3).

American Cinematographer

18 (April, 1937), No. 4
Dodd Describes B-M's New Type 24-Inch Sunspot

(p. 134). L. E. DODD

Mitchell Announces New Sound Recorder (p. 138).
Art Reeves Introduces All-Purpose Developer (pp.

142-143, 147, 172).
General Electric Announces 100-Watt Lamp Giving

Continuous Flashes (p. 168).

Bell Laboratories Record

15 (April, 1937), No. 8
A New Noise Meter (p. 252). J. M. BARSTOW

Electronics

10 (April, 1937), No. 4

The Acoustical Labyrinth (pp. 24-27, 36). B. J. OLNEY

Efficiency of Horn Loud Speakers (p. 30). F. MASSA

10 (May, 1937), No. 5

Noise in Frequency Modulation (p. 22). H. RODBR

Filmtechnik

13 (March 27, 1937), No. 5-6
A New German Hand Camera — "Arriflex" (Neuartige

Deutsche Handkamera) (p. 49). W. MARTINI

"Phonorhythm" (Fonorhythmie) (p. 50). P. HATSCHEK

13 (April 24, 1937), No. 7

Fragen zur Raumdarstellung (Questions on Stereo-
scopic Representation) (p. 61). G. TIMMERMANN
Neuer Richtmikrofone (New Directional Microphone)

(p. 63) P. HATSCHEK

99

100 CURRENT LITERATURE [J. s. M. P. E.

Neue Sicherheitsvorschriften fur Lichtspieltheater
(New Safety Recommendations for Motion Picture
Theaters) (p. 84). W. GUNTHER

Kinobild mit Gluhlampenfeldern (Motion Pictures by

Means of Panels of Incandescent Lamps) (p. 88). P. HATSCHEK

International Photographer

9 (May, 1937) No. 4

New Economical Trick Shot Camera (p. 5).
Twentieth Century-Fox Silent Camera Proven Success (p. 10).
New Canady Recording Galvanometer (p. 19).

9 (June, 1937), No. 5
Color Make-Up (p. 27).
"Preview" Moviola Ready for Use (p. 28).

International Projectionist

12 (April, 1937), No. 4

New Amplifier Features Reflect Rapid Progress in

Design (p. 7). L. CHADBOURNH

Projection Requisites of the Berthon-Siemens Lenticu-
lar Color-Film (p. 18). E. GRETENER

The Push-Pull Sound Recording and Reproducing

System (p. 19). F. T. JAMEY, JR.

12 (May, 1937), No. 5

Film Scratches (p. 7).

A New Projection Tool: The Cathode-Ray Oscillo-
scope (p. 12). L. P. WORK

Effect of New Recordings on Theater Sound Repro-
duction (p. 16). L. CHADBOURNE

A New Zero-Current Meter for Projection Room Use

(p. 22). R. GARWIN

Kinematograph Weekly

242 (April 1, 1937), No. 1563

A New Color Process Employing Quarter-Size Images
(p. 50).

Kinotechnik

19 (April, 1937), No. 4

Consideration of the Question of Satisfactory Illumi-
nation in Projection (Betrachtungen zur Frage der
gunstigsten Projektionsbildbeleuchtung) (p. 67). O. REEB

The Cameraman's Technical Demands of Raw Film,
Studio, Printing Establishment, and Theater (Die
filmtechnischen Anspruche des Kameramanns an
Rohfilm, Atelier, Kopieranstalt, und Filmtheater)
(p. 76). A. VON LAGORIO

Arriflex, A New Professional Hand Camera (Die Arri-
flex, eine neue Berufshandkamera) (p. 85).

July, 1937] CURRENT LITERATURE 101

Outline of Film Standardization (Grundlinien der- Nor-

mung im Film) (p. 91). W. RAHTS

19 (May, 1937), No. 6

Color-Film and Projection (Farbfilm und Projektion)

(p. 121). W. PAPE

Ufacolor Process (Das Ufacolor-Verfahren) (p. 125). G. IGNATOW

Mirror Reflecting Device on Motion Picture Cameras
(Die Spiegelreflexeinrichtung bei Kinokameras)
(p. 129). G. SEEBE-R

Floodlights and Spots with Fresnel Lenses (Schein-
wefer und Spots mit Stufenlinsen) (p. 130). G. O. STINDT .

Distortion as Produced by the Variation in Illumina-
tion along a Scanning Slit (Der optische Klirrfaktor
von Lichtspaltanordnungen ) (p. 132). A. D. JOTZOFF

Motion Picture Herald (Better Theaters Section)

127 (May 1, 1937), No. 5

How the New Developments in Sound Affect Mainte-
nance (p. 28). A. NADELL

127 (May 29, 1937), No 9
Theater Acoustics Today: Auditorium Form Factors

(p. 41). C. C. POTWIN

Photographic Journal

77 (April, 1937) (new series)

Photographic Progress During 1936 (p. 193). G. E. MATTHEWS

Progress in Colour Photography (p. 224). D. A. SPENCER

The Story of the Cartoon Film (p. 229). E. A. DYER

Increase in Technical Facilities for British Film Pro-
duction (p. 233). I. D. WRATTEN
Developments in Kinematographic Apparatus (p. 238). R. H. CRICKS
Studio Lighting for Kinematography (p. 245). B. LANGLEY
Negative-Positive Processing of Dufaycolor Film (p.

250). G. B. HARRISON

D. A. SPENCER

Photographische Industrie

35 (March 31, 1937), No. 13

High-Speed Camera Taking from 16 to 80,000 Pictures
per Second (Der Zeitdehner der Technik fur 80,000
bis 16 Aufnahme in der Sekunde) (p. 391).

35 (April 7, 1937), No. 14

Stability Testing of Motion Picture Films by Artificial
.Aging (Haltbarkeitsprufung von Kinofilmes durch
kunstliche Alterung) (p. 417).

35 (April 14, 1937), No. 15
Film Fires (Einiges iiber den Filmbrand) (p. 443). W. NAUCK

35 (April 21, 1937), No. 16
Sound Recording by the "Phonorhythm" Method (Die

102

CURRENT LITERATURE

[J. S. M. P. E.

Tonbildaufnahmen nach dem Phonorhythmiever-
fahren) (p. 467).

35 (May 19, 1937) No. 35

Die Bezugsebene fur Distanzeinstellung bei Schmal-
film-Kinoapparaten (The Relative Plane for Focal
Setting in Substandard Motion Picture Cameras)
(p. 581).

Proceedings of the Institute of Radio Engineers

25 (April, 1937), No. 4

Characteristics of American Broadcast Receivers as
Related to the Power and Frequency of Transmitters
(p. 387).

Multiple Amplifier (p. 421).

Frequency Modulation Noise Characteristics (p. 472).

Radio Engineering

17 (April, 1937), No. 4

Equipment and Methods Used in Routine Measure-
ments of Loud Speaker Response, II (pp. 16-18, 25).
The Isochrometer (p. 22).

17 (May 1937) No. 5

Equipment and Methods Used in Routine Measure-
ments of Loud Speaker Response (p. 22).

La technique cinematographique

9 (March, 1937), No. 75

A New Optical Projection Printing Process for Lenticu-
lated Film in Color Motion Picture Photography
(Un Nouveau Procede de Copie par Projection Op-
tique de Films Gauffres pour la Cinematographic en
Couleurs) (p. 881).

9 (April, 1937), No. 75

Qu'est-ce que la Solution Thomson-Houston-DeLassus?
(What Is the Thomson-Houston-DeLassus Solu-
tion?) (p. 903).

L'eclairage du film dans le lecteur de son (Optical
Systems for Sound-Films) (p. 911). .

La Cinematographic Francaise

19 (April 30, 1937), No. 965

L'Effet Photo- Electrique et Son Application aux
Cellules (Photoelectric Effect and Its Application to
Cells) (p. 1).

Television

10 (April, 1937), No. 110
We See Scophony's Latest System (p. 196).

C. FORSCH

S. JASIENSKI

A. VAN DYCK
D. E. FOSTER

L. A. KUBETSKY

M. G. CROSBY

S. V. PERRY

S. V. PERRY

J. DE LASSUS ST.-

GENIES

C. NORDMANN

J. P. CORTEX

C. TEVES

July, 1937]

CURRENT LITERATURE

103

Scanning Faults and How to Remedy Them (p. 200). G. PARR
Transformers for Television Scanning (p. 209). G. A. V. SOWTER

The Design of Vision- Frequency Amplifiers, II (p. 220). P. NAGY

10 (May, 1937), No. Ill

Magnetic Scanning Defects and Their Causes (p. 268). I. G. MALOFF
The First Acorn Valve Receiver for Vision Signals

(p. 273).
The Design of Vision-Frequency Amplifiers, III

(p. 279). P. NAGY

HARRY PFANNENSTIEHL

Harry Pfannenstiehl, a member of the Technical Staff of Bell Tele-
phone Laboratories, and of the Society of Motion Picture Engineers,
died suddenly on May 29, 1937, of heart trouble, from which he had
suffered for several years. He was born in New York City on April
24, 1887. His father was Adolph L. and his mother, Anna N. (Dossen-

H. PFANNENSTIEHL

bach) Pfannenstiehl, both of whom were born in Germany, but who
had moved to the United States during their youth.

In March, 1911, he joined the Engineering Department of the
Western Electric Company with whom he continued until 1925, when
the Bell Telephone Laboratories was formed. He had been with the
Laboratories continuously until his death, thus completing over
twenty-six years with the Bell System.

In April, 1913, he was transferred by the Western Electric Com-
pany to their branch in Antwerp, Belgium,- where he was employed
for about a year and a half.
104

HARRY PFANNENSTIEHL 105

Since the World War, Mr. Pfannenstiehl- had been engaged in a
considerable number of special developments for the Western Elec-
tric Company and Bell Telephone Laboratories where the design of
equipment has involved unusual problems with respect to ingenuity
of operating mechanisms, choice of materials for dynamic properties,
or extreme precision requirements. In the early developments of
the printing telegraph, he played a very substantial part. He was
principally responsible for the mechanics not only of telephoto trans-
mitting and receiving machines of 1925, but also of the recent tele-
photo equipment used by the Associated Press.

To the commercializing of sound picture apparatus, he contributed
by responsibility for much of the design of studio sound recording
machines and of theater sound-projecting equipment. In this work
he made a specialty of devices for driving the film uniformly; and
many of the improvements in sound quality that have resulted from
the recent perfection of these machines are attributable to his skill.

Mr. Pfannenstiehl contributed many papers to the scientific litera-
ture, several of which have been published in the JOURNAL of the
Society.

HIGHLIGHTS OF THE SPRING CONVENTION

HOLLYWOOD ROOSEVELT HOTEL

HOLLYWOOD, CALIF.

MAY 24-28, 1937

As Conventions come and go it would seem that each is more successful than
the preceding. However, it can be safely stated that the recent Convention in
Hollywood was by far the most successful of all that have been held by the Society
on the western coast, and it is doubtful whether any other Convention has ever
exceeded this one in point of interest, attendance, and participation. The number
of paid registrations was greater than at all previous conventions, and the at-
tendance at the technical sessions, from the first session on Monday morning to
the last session on Friday evening, was indicative of the increasing interest of
the Hollywood engineers and technicians in the activities of the Society.

The evening sessions were especially interesting and capacity audiences were
attracted to each one. The gratitude and appreciation of the Society and the
Board of Governors was expressed by President Wolf in his closing remarks on
Friday evening to the Society officers on the West Coast, to the Board of Managers
of the Pacific Coast Section, and to the officers of the Research Council of the
Academy of Motion Picture Arts & Sciences. One of the highlights of the week
was the special Thursday evening session of the Academy Research Council, ar-
ranged through the courtesy of William Koenig, Chairman, and Nathan Levinson,
Vice- Chairman of the Council. The Society is also greatly indebted to Gordon
S. Mitchell, Manager of the Research Council, and the members of his staff for
their excellent cooperation and generous assistance.

TECHNICAL SESSIONS

The Convention opened at 10 A.M. on Monday (May 24th) with a brief presi-
dential address by Mr. S. K. Wolf; several Committee reports, including the
comprehensive Progress Committee's Annual Report; and two papers on applica-
tions of motion pictures.

The customary Informal Luncheon was held at noon in the Florentine Room of
the Hotel, during which the members of the Society were addressed briefly by
President Wolf and Major Nathan Levinson, of Warner Bros. Studios, Raymond
Hatton, well known comedian, and various members of the Board of Managers
of the Pacific Coast Section. An official photograph of the delegates was made on
the Patio immediately following the luncheon.

The highlight of the Monday afternoon session, which dealt with studio mat-
ters, was probably the paper describing "A New Viewpoint on the Lighting of
Motion Pictures," by G. Gaudio, well known cinematographer of Hollywood. In
arriving at his new view-point in lighting technic, Mr. Gaudio first traced the de-
velopment of the studio lighting art to show the gradual evolution of the technic
into its present-day form. Other papers, as listed in the program printed on the
following pages, completed a well-rounded session on the engineering problems
106

FALL CONVENTION 107

and developments in modern motion picture studios. - The paper by L. Fermaud,
describing "The London Film Studios at Denham, England" was particularly in-
teresting in this respect.

The evening of Monday, May 24th, was devoted to an all-Technicolor program
of recent feature and short subjects, including the new release A Star Is Born.
This entire session was arranged through the courtesy of Mr. G. F. Rackett,
Vice-President of Technicolor Motion Picture Corporation.

The morning of Tuesday, May 25th, was devoted to the problems of color motion
pictures. Considerable interest was shown in the papers dealing with the new
Agfacolor process and color-print processes. In connection with the latter presen-
tation, by O. O. Ceccarini,' a comprehensive exhibit of color-stills by various
studios and leading color photographers throughout the country was on display
in one of the parlors of the Hotel during the entire Convention.

The afternoon session was marked by a particularly interesting paper by H. E.
A. Joachim, of Dresden, Germany, describing "Twenty Years of Development
of High-Frequency Cameras." The latter part of the afternoon was devoted to
a symposium on transmission meters, and provided considerable technical ma-
terial on up-to-date methods of recording and measuring sound transmission
characteristics.

One of the most outstanding — some would perhaps say the most outstanding —
sessions of the Convention was the one held at the Universal Studios on the
evening of Tuesday, May 25th, at which a complete demonstration was given of
"How Motion Pictures Are Made." A complete description of the proceedings
of the evening will be published in a forthcoming issue of the JOURNAL, but it is
well at this point to register the thanks of the Society to those who worked so hard
to make the evening an outstanding success. Thanks are due particularly to Mr.
Charles R. Rogers, Vice-President in Charge of Production, and to Mr. Homer
G. Tasker, Sound Supervisor of the Universal Studios.

About 450 or 500 delegates and their friends assembled at 8 P.M. on one of the
sound stages, where they were welcomed to Universal by Mr. Val Paul, Studio
Manager. Then followed a paper by Mr. Robert Presnell, Associate Producer,
in which were described the methods and problems involved in preparing stories
for production. With particular reference to a scene in the forthcoming picture,
One Hundred Men and a Girl, starring Deanna Durbin, a paper by John Harkrider,
Supervising Art Director (presented by Michael Fitzmaurice), discussed the
problem of "Set Design from Script to Stage." An artist and an architectural
member of the studio demonstrated with crayon and pencil how the preliminary
sketches are made in planning the sets to conform to the ideas of the authors of
the stories. Then followed a paper by Bernard Brown, Chief Music and Dubbing
Mixer, on "Prescoring for Song Sequences." The procedure as described in the
paper was demonstrated by an actual recording of the voice of Miss Deanna
Durbin singing a song to a playback orchestral accompaniment which was later
to be dubbed into the picture shot on the stage designed by the artists as described
above.

Adjourning now to the projection stage, the members were treated to a complete
demonstration of how motion pictures are photographed. A complete crew of
cinematographers, lighting men, director, and actors (Mischa Auer and Deanna
Durbin) all participated in demonstrating the procedure, to the accompaniment

108 FALL CONVENTION [J. s. M. P. E.

of an informal description of the procedure by Mr. Tasker. When the shot was
completed, the group again convened on the sound stage and saw the projection of
the completed picture which had been photographed and recorded as here de-
scribed. (It is hardly necessary to state, of course, that the finished scene, as
projected, was not the actual one shot during this evening's session; such would
have been impossible in view of the time required for processing, etc.)

Concluding the evening, various shots were projected to show the effects upon
the "mood" of the picture of various kinds of background music, as discussed by
Charles Previn, Musical Director, and to demonstrate also the manner of rough
cutting and editing pictures, as described by Maurice Pivar, Supervising Editor.
A particularly interesting demonstration was given 'by Edwin Wetzel, Dubbing
Mixer, during which he went through the actual procedure of mixing a number
of sound effects into a picture that was projected first with dialog only and later
with the sound effects added.

The morning of Wednesday, May 26th, was devoted principally to acoustic <
and sound, one of the outstanding papers of the session being the one on "Recent
Progress in Acoustics," by V. O. Knudsen. The papers on an "Improved Noise-
Reduction System," by Hasbrouck, Baker, and Batsel, and on "A Device for
Direct Reproduction from Variable- Density Sound Negatives," by M. J. Alber-
sheim, aroused considerable interest among those attending the meeting.

The afternoon of Wednesday was devoted to a visit to the Studios of the
Twentieth Century-Fox Film Corporation at Beverley Hills, during which the
members were escorted throughout the lot and the various stages.

The Semi-Annual Banquet was held in the Blossom Room of the Hotel on the
evening of the same day. The evening was devoted in its entirety to dining and
entertainment, as it was felt that the rigors of the long technical sessions war-
ranted dispensing with formalities on that evening.

Thursday afternoon (May 27th) was devoted to papers and presentations deal-
ing with laboratory and projection problems. A paper by Captain J. G. Bradley,
dealing with the "Changing Aspects of the Film Storage Problem," contained in-
teresting information on experiments recently conducted with regard to the in-
flammability of film in storage cabinets. A paper by J. M. Nickolaus on "Toning
Positive Film by Machine Methods" described the procedure followed in toning
the recent feature The Good Earth at the Metro-Goldwyn-Mayer Studios. The
session included also papers on the design of a densitometer and the measurement
of density and graininess, which aroused considerable discussion, and on the ap-
plication of pH. control to photographic fixing baths and other solutions.

Another outstanding session of the Convention was held on the evening of
Thursday at the M-G-M Studios at Culver City; namely, a meeting of the Re-
search Council and the Technicians Branch of the Academy of Motion Picture
Arts & Sciences, to which the members and guests of the SMPE were invited.
An outstanding presentation of the evening was the paper on "The Work of the
Committee on Standardization of Theater Sound Projection Equipment Char-
acteristics," by J. K. Hilliard, Chairman of the Academy Committee. This
paper described the work of the Committee in connection with the establishment
of theater equipment characteristics. The evening concluded with the projection
of a number of scenes from outstanding films, illustrating sound quality, special
effects, and unusual photography.

July, 1937] FALL CONVENTION 109

The morning session of Friday, May 28th, was devoted to an apparatus sym-
posium and miscellaneous papers on magnetic recording, the use of infrared nega-
tive, laboratory equipment, etc. The afternoon of Friday was devoted to a group
of papers on 16-mm. and 35-mm. sound recording and reproduction, including the
report of the Standards Committee, and a description of the new SMPE 16-mm.
Sound Test-Film, by M. C. Batsel. A new 16-mm. sound projector was described
and demonstrated effectively by E. C. Fritts and O. Sandvik and examples of
very fine class A push-pull recordings were demonstrated by G. L. Dinunick.

The closing session of the Convention on Friday evening, at which Mr. Ralph
R. Beal, Research Supervisor of the Radio Corporation of America, presented a
description of the RCA system of television, was attended by perhaps 450 or 500
members and guests of the Society.

ACKNOWLEDGMENT

As pointed out previously, the success of the Convention was due to the efforts
of a large number of officers, members, and friends of the Society. Credit is due
particularly to the efforts of Mr. W. C. Kunzman, Convention Vice-President;
Mr. H. G. Tasker, Past-President; Mr. J.I. Crabtree, Editorial Vice-President;
Mr. G. E. Matthews, Chairman, Papers Committee; Messrs. H. Griffin and J.
Frank, Jr., in charge of projection facilities; Mr. W. A. Mueller, Chairman; and
Mr. L. A. Aicholtz, Secretary, West Coast Local Papers Committee; to the Board
of Managers of the Pacific Coast Section; Mr. K. F. Morgan, Chairman; Mr. G. F.
Rackett, Past Chairman of the Section, and Executive Vice-President of the Society;
Mr. G. A Chambers, Secretary-Treasurer; and Messrs. J. O. Aalberg and H. W.
Moyse, Managers. The officers and members of Los Angeles Local No. 150
I.A.T.S.E. are particularly to be thanked for their generous assistance in con-
nection with the projection of all the motion pictures throughout the entire Con-
vention session. Appreciation is also expressed to the American Society of Cine-
matographers for supplying a number of papers by members of their Society.

Acknowledgement for their generous assistance is also due to P. Mole, Chairman,
Local Arrangements Committee; Mrs. K. F. Morgan and Mrs. P. Mole, hostesses;
and Messrs. C. W. Handley, E. Huse, and G. F. Rackett, for their assistance in
connection with transportation, hotel accommodations, banquet, etc.

Among the companies and studios that should be thanked for their coopera-
tion in providing various facilities of the Convention, and for their great cordiality
in receiving the members at the studios, are the following: National Carbon
Company; International Projector Corporation; National Theater Supply Cor-
poration; Raven Screen Company; Electrical Research Products, Inc.; Bausch
& Lomb Optical Company; General Electric Company ; Mole Richardson, Inc.;
Enterprise Optical Company; General Electric Supply Company; and Dicta-
phone Products Corporation, all of which collaborated in making available the
equipment used during the technical sessions. Universal Studios, M-G-M
Studios, and Twentieth Century-Fox Film Studios are to be thanked for enter-
taining the delegates and making available the facilities of their plants. Thanks
are due also to the Fox West Coast Theaters, Warner Bros. Hollywood Theater,
and Pantages Theater for supplying passes to members and guests during the
week of the Convention, and to Warner Bros. Studios for supplying the enter-
tainment features for the banquet

PROGRAM*

SPRING, 1937, CONVENTION, HOLLYWOOD, CALIF.
HOLLYWOOD-ROOSEVELT HOTEL

MONDAY, MAY 24th

9:00 a. m. Business and General Session. G. F. Rackett, Chairman.

10:00 a. m. Opening Remarks by President S. K. Wolf.

Report of the Convention Committee; W. C. Kunzmann, Conven-
tion Vice- President.

Report of the Membership Committee; E. R. Geib, Chairman.

Report of the Papers Committee; G. E. Matthews, Chairman.

"Progress in the Motion Picture Industry:" Report of the Progress
Committee; J. G. Frayne, Chairman.

Report of the Historical Committee; E. Theisen, Chairman.

"Soft X-Ray Motion Pictures of Small Biological Specimens;"
H. F. Sherwood, Kodak Research Laboratories, Rochester, N. Y.
(Demonstration.)

"Educational Film Progress and Problems;" S. K. Wolf, Erpi
Picture Consultants, Inc., New York, N. Y. (Demonstration.)

12:30 p. m. Informal Luncheon.

Studio Session. K. F. Morgan, Chairman.
2:00 p. m. "The London Film Studios at Denham, England;" L. C. Fermaud-

London Film Productions, Ltd., Denham, Middlesex, England.
"The Evolution of Special- Effects Photography from an Engineering

Viewpoint;" F. W. Jackman, Hollywood, Calif. (Demonstration.)
"Special Engineering Problems in a Motion Picture Studio;"

W. Strohm, Twentieth Century-Fox Film Corp., Hollywood,

Calif.
"A New Viewpoint on the Lighting of Motion Pictures ;" G. Gaudio,

A. S. C., Hollywood, Calif. (Demonstration.)
"Recent Developments in Motion Picture Set Lighting Equipment ;"

E. C. Richardson, Mole-Richardson, Inc., Hollywood, Calif.
"Light-Weight Stage Pick-Up Equipment;" L. D. Grignon, Para-
mount Productions, Inc., Hollywood, Calif.

8:30 p. m. An all-Technicolor program of recent feature and short subjects.
TUESDAY, MAY 25th

Color Session. J. A. Ball, Chairman.

10:00 a. m. "Color Print Processes;" O. O. Ceccarini, Metro-Goldwyn-Mayer
Studios, Culver City, Calif. A comprehensive exhibit of color

* As actually followed at the meetings.
110

FALL CONVENTION 111

stills by various studios and leading color photographers through-
out the country was on display during the Convention by the
following contributors:

APEDA STUDIOS PAUL A. HESSE STUDIOS

New York New York

O. O. CECCARINI HEWETT & KEENE

M-G-M Studios, Hollywood New York

DEFENDER PHOTO SUPPLY Co. WILLIAM G. HOUSKEEPER

Rochester South Orange, N. J.

JAMES N. DOOLITTLE CHARLES H. MILLER

Los Angeles Chicago

EASTMAN KODAK Co. NICHOLAS MURAY

Rochester New York

GENERAL MOTORS CORP. PAGANO, INC.

Photographic Div., Detroit New York

STEICHEN
New York

"The New Agfacolor Process;" J. L. Forrest and F. M. Wing,

Agfa Ansco Corporation, Binghamton, N. Y.
Report of the Color Committee; J. A. Ball, Chairman.
"Advanced Technic of Technicolor Lighting;" C. W. Handley,

National Carbon Co., Cleveland, Ohio.
"Some Lighting Problems in Color Cinematography;" T. T. Baker,

Dufaycolor, Inc., New York, N. Y. (Demonstration.)

Instruments Session. Douglas Shearer, Chairman.

2:00 p.m. "Twenty Years of Development in High-Frequency Cameras;"
H. E. A. Joachim, Zeiss-Ikon Aktiengesellschaft, Dresden,
Germany.

"A High-Precision Sound-Film Recording Machine;" H. Pfannen-
stiehl, Bell Telephone Laboratories, Inc., New York, N. Y.

"A Dynamic Light-Valve;" E. Gerlach, Klangfilm G. m. b. H.,
Berlin, Germany.

"A Laboratory Flutter-Measuring Instrument;" R. R. Scoville,
Electrical Research Products, Inc., Hollywood, Calif.

"Power Level Indicator for Sound Recording;" F. L. Hopper, Elec-
trical Research Products, Inc., Hollywood, Calif.

Symposium on Transmission Meters.

4:00 p. m. "A Transmission-Measuring System Utilizing a Graphic Recording
Meter;" W. W. Lindsay, Jr., General Service Studios, Holly-
wood, Calif. •

"A New Instrument for Producing Automatically a Graphic Record
of Audio-Frequency Characteristics;" A. D. MacLeod, Tobe
Deutschmann Corporation, Canton, Mass. (Demonstration.)

"A Continuous Level Recorder for Routine Studio and Theater

112

FALL CONVENTION

[J. S. M. P. E.

Measurements;" G. M. Sprague and J. K. Milliard, Metro-
Goldwyn-Mayer Studios, Culver City, Calif.

"A Curve-Plotting Transmission Meter;" L. A. Aicholtz, Universal
Pictures Corporation, Universal City, Calif.

"A Curve-Plotting Transmission Meter;" L. D. Grignon, Para-
mount Productions, Inc., Hollywood, Calif.

8:00 p. m. Studios of Universal Pictures Corporation, Universal City, Calif. ;

Special Evening Demonstration: "How Motion Pictures

Made." Homer G. Tasker, Chairman.
Assemble on Stage 10.
Motion Picture Cartoon.

Welcome to Universal — Val Paul, Studio Manager.
"Preparing a Story for Production;" Robert Presnell, Associate

Producer. (Story conference, shooting scripts, scheduling players,

and equipment.)
"Prescoring for Song Sequences;" Bernard Brown, Chief Music

and Dubbing Mixer. (Demonstration.)
"Set Design from Script to Stage," illustrated by the set used for

remainder of this program; John Harkrider, Supervising Art

Director. Presented by Michael Fitzmaurice. (Demonstration)
Adjourn to production stage.
"Production Handling of Lighting Equipment;" Frank Graves,

Superintendent Electrical Department. (Demonstration.)
"Lighting a Long Shot and Close-Up;" Joe Valentine, Director of

Photography. (Demonstration.)

"Sound Pick-Up on a Long Shot and Close-Up;" Joe Lapis, Pro-
duction Mixer. (Demonstration.)
"The Director's Problem;" Joseph Pasternak, Associate Producer.

( Demonstration . )
Return to Stage 10.

Projection of "dailies" made in the demonstration above.
"Editing Motion Pictures;" Maurice Pivar, Supervising Editor.

(Demonstration.)
"Setting Music to Motion Pictures;" Charles Previn, Musical

Director. (Demonstration.)
"Assembling a Final Sound-Track;" Edwin Wetzel, Dubbing

Mixer. (Demonstration.)

WEDNESDAY, MAY 26th

Acoustics and Sound Session. William Mueller, Chairman.
10:00 a. m. "Recent Progress in Acoustics;" V. O. Knudsen, Professor of

Physics and Dean of Graduate Study, University of California,

Los Angeles, Calif.
"Mathematical Relations between Grain, Background Noise, and

Characteristic Curve of Sound-Film Emulsions;" W. J. Albers-

heim, Electrical Research Products, Inc., New York, N. Y.

July, 1.937] FALL CONVENTION 113

"Improved Noise-Reduction System for High-Fidelity Recording;"
H. J. Hasbrouck, J. O. Baker* and C. N. Batsel, RCA Manu-
facturing Co., Inc., Camden, N. J., and Hollywood, Calif.

"A Device for Direct Reproduction from Variable-Density Sound
Negatives;" W. J. Albersheim, Electrical Research Products,
Inc., New York, N. Y.

"Sound Pick-Up Methods for Motion Pictures;" J. P. Maxfield,
A. W. Colledge, and R. T. Friebus, Electrical Research Products,
Inc., New York, N. Y.

"A Dubbing Rehearsal Channel;" H. G. Tasker, Universal Pictures
Corp., Universal City, Calif.

"An Automatic Sound-Track Editing Machine;" G. M. Best,
Warner Brothers Pictures, Inc., Burbank, Calif.

2:30 p. m. Visit to Twentieth Century-Fox Film Corporation, Beverly Hills,
Calif.

7:30 p. m. Blossom Room; Semi- Annual Banquet.
THURSDAY, MAY 27th

10:00 a. m. Open Morning.

Laboratory and Projection Session. Harry Ensign, Chairman.
1:10 p. m. "Changing Aspects of the Film Storage Problem;" Capt. J. G
Bradley, National Archives, Washington, D. C. (Demonstration.)

Report of the Projection Practice Committee; H. Rubin, Chairman.

Report of the Exchange Practice Committee; A. W. Schwalberg,
Chairman.

"A Wide-Range Linear-Scale Photoelectric Cell Densitometer ;"
W. W. Lindsay, Jr., General Service Studios, Inc., Hollywood,
Calif., and W. V. Wolfe, RCA Manufacturing Co., Inc., Holly-
wood, Calif.

"Standardization of Photographic Density;" C. M. Tuttle and
A. M. Koerner, Kodak Research Laboratories, Rochester, N. Y.

"Objective Quantitative Determination of Graininess in Photo-
graphic Emulsions;" A. Goetz, Associate Professor of Physics,
and W. O Gould, California Institute of Technology, Pasadena,
Calif.

"Sound-Track Blooping;" F. D. Williams, Williams Laboratory,
Hollywood, Calif. (Demonstration.)

"Toning Positive Film by Machine Methods;" J. M. Nickolaus,
Metro-Goldwyn-Mayer Corporation, Culver City, Calif. (Dem-
onstration.)

"Fixing Baths and Their Properties;" J. I. Crabtree, H. Parker, Jr.,
and H. D. Russell, Kodak Research Laboratories, Rochester,
N. Y.

"Practical Applications of pH Control in Motion Picture Process-
ing;" D. K. Allison, Chemical and Research Corporation, Holly-
wood, Calif.

114 FALL CONVENTION [J. S. M. p.

8:00 p. m. Metro-Goldwyn-Mayer Studios, Culver City, Calif.

Meeting of the Research Council and the Technicians' Branch

the Academy of Motion Picture Arts and Sciences; William Kc
Chairman, Research Council; Major N. Levinson, Vice- Chair
man, Research Council, and Chairman, Technicians' Branch.

"Observations on Hollywood Production in Relation to the
duction of Army Training Films;" Capt. R. T. Schlosberg, U.
Army Signal Corps ; now on duty as a student with the Academj
of Motion Picture Arts and Sciences.

"Cooperative Technical Program of the Research Council of tl
Academy of Motion Picture Arts and Sciences;" W. Koenig,
Chairman, Research Council.

"The Work of the Committee on Standardization of Theater Sound
Projection Equipment Characteristics;" J. K. Milliard, Chairman.
(Demonstration.)

Projection and Discussion of Outstanding Films Illustrating
Sound Quality, Special Effects, Unusual Photography. Ar-
ranged by the technicians of the Hollywood studios.

FRIDAY, MAY 28th

Apparatus Symposium, Peter Mole, Chairman.

10:00 a. m. "The Super Simplex Pedestal;" J. Frank, Jr., International Pro-
jector Corporation, New York, N. Y.

"Complete Cue-Mark Elimination Plus an Automatic Change-
Over;" J. P. Pollanz and S. A. MacLeod, Los Angeles, Calif.

"Magnetic Recording-Reproducing Machine for Objective Speech
Study;" S. J. Begun. New York, N. Y. (Demonstration.)

"Infrared Negative as Applied to Special-Effects Photography;"
G. W. Hough and W. Leahy, Agfa Ansco Corporation, Holly-
wood, Calif. (Demonstration.)

"Laboratory Equipment for the Smaller Laboratory;" Arthur
Reeves, Hollywood, Calif.

"Two New Films for Duplicating Work;" Eastman Kodak Com-
pany, Hollywood, Calif. (Demonstration.)

"A New Type Double-Film Attachment;" E. C. Manderfeld,
Electrical Research Products, Inc., Hollywood, Calif.

"A Combined Viewing and Projection Machine with or without
Sound;" I. Serrurier, Moviola Co., Hollywood, Calif. (Demon-
stration.)

Sound Equipment Symposium. £. H. Hanson, Chairman.
2:00 p. m. "Present Aspects in the Development of 16-Mm. Sound;" A.
Shapiro, The Ampro Corporation, Chicago, 111. (Demonstration.)

Report of the Non-Theatrical Equipment Committee; R. F.
Mitchell, Chairman.

"The SMPE 16-Mm. Sound Test-Film;" M. C. Batsel. (Demon-
stration.)

July, 1937] FALL CONVENTION 115

"A Sound Kodascope;" E. C. Fritts and O. Sandvik, Eastman

Kodak Company, Rochester, N. Y. (Demonstration.)
Report of the Standards Committee; E. K. Carver, Chairman.
Report of the Sub-Committee on Film Perforation; J. A. Dubray,

Chairman.
"A Combination Picture and Non-Slip Ultraviolet Automatic

Printer;" O. B. Depue, Chicago, 111. (Demonstration.)
"The RCA Recording System and Its Adaptation to Various Types

of Sound-Track, with Demonstration of Recent Recordings of the

Class A Push-Pull Type;" G. L. Dimmick, RCA Manufacturing

Co., Inc., Camden, N. J.
"A Linear Decibel Scale Volume Indicator;" F. G. Albin, United

Artists Studio Corporation, Hollywood, Calif.

8:00 p. m. Television Session. S. K. Wolf, Chairman.

"RCA Developments in Television;" Ralph R. Bcal, Research
Supervisor, Radio Corporation of America, New York, N. Y.

(Illustrated with slides and motion pictures.)

SOCIETY ANNOUNCEMENTS

FALL, 1937, CONVENTION

The next Convention of the Society will be held at New York, N. Y., at the
Hotel Pennsylvania, October llth to 14th, inclusive. Work has already been
begun by the Papers Committee under the Chairmanship of G. E. Matthews,
and members are urged to take advantage of this early announcement of the
dates of the Convention by giving some thought to the presentations and demon-
strations they may wish to make. All those having such plans in mind should
communicate as early as possible with the Chairman of the Papers Committee.

Special hotel rates, guaranteed to SMPE delegates, European plan, will be as
follows:

One person, room and bath $ 3.50

Two persons, double bed and bath 5.00

Two persons, twin beds and bath 6.00

Parlor suites 1 1 .00 up

Room reservation cards will be mailed to the membership of the Society in the
near future, and everyone who plans to attend the Convention should return his
card to the Hotel promptly in order to be assured of satisfactory accommodations.
Special garage rates will be provided for SMPE delegates who motor to the
Convention.

NOMINATIONS FOR OFFICE

Ballots for nomination of Officers of the Society for 1938 have already been
mailed to the voting membership of the Society, and final nominations will be
made by the Board of Governors at the next meeting, to be held on July 9th at
New York.

Officers and Governors whose terms expire December 31, 1937, are as follows:

G. F. RACKETT, Executive Vice-President
L. A. JONES, Engineering Vice-P resident
O. M. GLUNT, Financial Vice-President
J. FRANK, JR., Secretary
L. W. DAVEE, Treasurer
A. S. DICKINSON, Governor
A. C. HARDY, Governor
H. GRIFFIN, Governor

The Executive Vice-President, Secretary, and Treasurer are to be elected for
one-year terms; the remaining officers for two-year terms.

116

SOCIETY ANNOUNCEMENTS
PROGRESS AWARD COMMITTEE

117

As announced in the previous issue of the JOURNAL, the next meeting of the
Progress Award Committee will be held on July 6th, at which time all nominations
for the Progress Medal received by the Committee will be considered, and the
Committee's report to the Board of Governors drafted.

The regulations pertaining to the Progress Award were given in detail in the
June issue of the JOURNAL.

ADMISSIONS COMMITTEE

At a recent meeting of the Admissions Committee, at the General Office of the
Society, the following applicants for membership were admitted to the Associate
grade :

AGINS, S. B.

1116 N. New Hampshire St.,

Los Angeles, Calif.
BALL, A.

Kiev Ulitza Korolenko,
dom 34, kv. 2,
U. S. S. R.
BELL, D. G.
6910 San Mateo Blvd.,

Dallas, Texas.
BYARS, T.
605 N. Ervay St.,

Dallas, Texas.
DECKER, C.

166 Washington St.,

Binghamton, N. Y.
HELMER, R.
.5312 244th St.,

Douglas ton, N. Y.
KAWAGUCHI, T.

117 N. San Pedro St.,

Los Angeles, Calif.
KELLY, F. J.
4109 Northcliffe Ave.,

Montreal, Canada.
LINCOLN, L.
45 E. 49th St.,

New York, N. Y.
Lix, E. C.

1369 N. Wilton Place,
Hollywood, Calif.

LUBCKE, H. R.

Don Lee Broadcasting System,
Seventh & Bixel Sts.,
Los Angeles, Calif.
MATHYS, G. J.
"The Moorings,"
Osborne Road,
Potters Bar,
Hertfordshire, England.
MILLAR, S. S.

Dominion Sound Equipments, Ltd.
820 Cambie St.,
Vancouver, B. C.
NELSON, R. G.
5436 School St.,
Chicago, III.

NlKITIN, J. I.

Monastyrskaja 11, Kiev,

U. S. S. R.
REASIN, W. H.
22 The Green,
Dover, Del.

ROSENTHAL, H.

232 Beach 141st St.,
Bell Harbor, N. Y.
THOMAS, W.

581 Monterey Road,

Glendale, Calif.
VAN VALKENBURGH, R. M.
506 W. 61st Place,
Chicago, 111.

118

SOCIETY ANNOUNCEMENTS

In addition, the following applicants have been admitted by vote of the Board
of Governors to the Active grade:

BATTLE, J. A.

Electrical Research Products, Inc.,
250 W. 57th St.,
New York, N. Y.

BONAMICO, C.

2 E. 86th St.,

New York, N. Y.
KELLEY, W. F.
1217 Taft Bldg.,

Hollywood, Calif.
KERNS, E. F.

The Museum of Modern
Art Film Library,
485 Madison Ave.,
New York, N. Y.

LAMBOIT, P.
47 W. 68th St.,

New York, N. Y.
MCLAUGHLIN, W. F.

Film Automatic Machine Corp.
17 Nelson St.,
Bloomfield, N. J.

POTTER, R. S.

Defender Photo Supply Co.
Driving Park,
Rochester, N. Y.

SKELLY, J. F.
Du Pont Club,
Parlin, N. J.

VOLKMANN, J. E.

RCA Manufacturing Co., Inc.,
Camden, N. J.

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX AUGUST, 1937 Number 2

CONTENTS

Page

RCA Developments in Television R. R. BEAL 121

Television from the Standpoint of the Motion Picture Produc-
ing Industry — Report of the Scientific Committee of the
Research Council of the Academy of Motion Picture Arts

& Sciences 144

Report of the Standards Committee 149

Report of the Western Museum Committee 151

Report of the Papers Committee 154

A New Viewpoint on the Lighting of Motion Pictures

G. GAUDIO 157

The Advanced Technic of Technicolor Lighting

C. W. HANDLEY 169

Recent Developments in Motion Picture Set Lighting

E. C. RICHARDSON 178
Power-Level Indicators for Sound Recording. . . .F. L. HOPPER 184

Light- Weight Stage Pick-up Equipment L. D. GRIGNON 191

Special Engineering Problems in a Motion Picture Studio

W. T. STROHM 197
New Motion Picture Apparatus

A High-Precision Sound-Film Recording Machine

H. PFANNENSTIEHL 202

A Laboratory Flutter-Measuring Instrument R. R. SCOVILLE 209
Magnetic Recording-Reproducing Machine for Objective

Speech Study S. J. BEGUN 216

Frederick Eugene I ves— 1856-1937 219

Current Literature 222

Fall Convention— New York, N. Y., October 11-14, 1937 224

Society Announcements 227

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS, EDITOR

Board of Editors

J. I. CRABTRBE, Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum; to members, $5.00 per annum,
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y.
Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers hi question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 100 E.42nd St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 463 West St., New York, N. Y.
Convention Vice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK, JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York, N. Y.

GOVERNORS

M. C. BATSEL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 250 W. 57th St., New York, N. Y.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE, 205 W. Wacker Drive, Chicago, 111.

RCA DEVELOPMENTS IN TELEVISION*
R. R. BEAL**

Summary. — A brief review is given of the studies made of the several characteristics
of television images and other factors that have been effective in establishing standards,
in determining satisfactory performance, and in guiding the step-by-step develop-
ment of the RCA electronic system of high-definition television.

The system employs the "Iconoscope," a cathode-ray tube for translating the visual
image into electrical impulses, and the "Kinescope" for transforming the electrical
impulses back into the variations of light-intensity to reproduce the image. The
sensitivity and characteristics of the "Iconoscope" as a pick-up device are discussed.

The fundamentals of the RCA high-definition television system now under ex-
perimental field test in the New York area and the standards presently employed are
reviewed. Photographs of the studios and other parts of the field-test facilities are
included. A brief review is given to indicate the progress made and the results at-
tained up to the present time in these field tests.

The technic of formulating and presenting television programs is peculiar to the
requirements of television. The development of the technic is presently related to
programs employing artists in studios, outside pick-ups, and motion picture film.
The requirements of program technic are discussed.

Television and motion pictures have in common the objective of
reproducing on a viewing screen images that appear to the eye to
have uninterrupted motion. While some of the fundamentals through
which this objective is attained in the two arts may be closely re-
lated, others are widely different. Objectively and to some extent
technically, the problems parallel in the illumination of the subject,
in creating the illusion of motion, in realizing an acceptable standard
of definition, and in obtaining appropriate brightness and size of re-
produced image on the viewing screen. An outstanding difference
appears in the system by which the reflected light from the subject
is transmitted to the viewing screen.

In motion pictures, the reflected light from the subject is converted
into a film record, and transmission from the film record to the view-
ing screen is effected through the agency of light. In television,

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
19, 1937.

** Supervisor of Research, Radio Corporation of America, New York, N. Y.

121

122

R. R. BEAL

[J. S. M. P. E.

transmission is effected through the agency of electricity. Reflected
light from the subject is converted into electrical impulses. These
may be transmitted by radio or by special cables from the point at
which the subject is located to a point far removed from that locality,
and then reconverted into light-images upon the viewing screen.
The reproduced image may originate from a subject or from a film
record of a subject.

The development of a television system by which images of high
definition may be transmitted electrically and reproduced on a view-
ing screen has required intensive research by RCA for a period of
more than ten years. This research has passed through many stages,
beginning with early mechanical arrangements and advancing to the

IMAGE OF VIEW
FALLS ON FRONT

of PHOTOCELLS

BANK Of PHOTOCELLS

EACH PH
ITS CO*
AN AMP

FIG. 1. Elements of the Carey system.

present all-electronic system now under field test in the New York
City area.

Some of the requirements of a high-definition system may be indi-
cated by a brief description of a system patterned after a suggestion
made by Carey about 1875. The elements of this system are illus-
trated in Fig. 1. A pick-up area is constructed of a bank of photoelec-
tric cells and a viewing screen of a like number of incandescent lamps.
Each photocell in the bank is connected by an electrical circuit
through an amplifier to the correspondingly positioned lamp in the
viewing screen. When the light-image to be transmitted is focused
upon the bank of photocells, electric current then will flow through
the circuits connecting those of the photocells that receive light to
the corresponding lamps in the viewing screen, and a reproduction
of the subject will appear as an illuminated picture.

In this system, the amount of detail that can be transmitted is
limited by the physical dimensions of the individual photocells in the
pick-up area. Each photocell represents an element of picture area,

Aug., 1937]

RCA DEVELOPMENTS IN TELEVISION

123

and the detail in any area of the picture smaller than the area of the
photocell can not be transmitted. An electrical circuit is required
to transmit information concerning the brightness of each ele-
ment of picture area. As the amount of detail increases, the num-
ber of electrical circuits increases. Such a multiple-circuit method
is not practicable for transmitting images electrically over long dis-
tances. A single channel must be employed for this purpose. This
requires methods that involve dividing the light into elements, con-
verting the illumination on each element into electrical impulses,

-jen fc r/N<f con. s
FIG. 2. Schematic arrangement of the Iconoscope

transmitting these impulses in orderly sequence, and reconverting
them into appropriately positioned light upon the viewing screen.

In the RCA high-definition television system, the first step in this
process occurs in the Iconoscope,* which converts the light-image
into electrical impulses, and the final step takes place in the Kine-
scope,* which transforms the electrical impulses into a light-image
upon the viewing screen.

The Iconoscope, illustrated in Fig. 2, consists of an electron gun
and a photosensitive mosaic in a highly evacuated glass envelope.
The electron gun produces a fine pencil or beam of electrons, which
is focused to a spot on the mosaic. This beam is moved horizontally

* Registered trade-marks of Radio Corporation of America.

124

R. R. BEAL

[J. S. M. P. E.

and vertically, and so caused to scan the mosaic. The motion of the
scanning beam is produced by appropriately applied electromagnetic
fields.

The mosaic consists of a vast number of tiny electrically isolated
photosensitized silver globules. These cover one side of a thin sheet
of mica. The other side of the mica is covered with a conducting
film, and this film is connected to a signal lead. The mosaic may be
thought of as a very large number of minute photocells, each of them
shunted by an electrical condenser which couples it to a common
signal lead. When the mosaic is illuminated, these condensers are
charged positively with respect to their equilibrium potential, due

FIG. 3. The Iconoscope.

to the emission of photoelectrons. This positive charge is pro-
portional to the quantity of light received. The electron beam, as
it scans the mosaic from left to right, drives to equilibrium the ele-
ments over which it passes, and thus releases the charges and induces
current impulses in the signal lead. The train of current impulses
thus generated constitutes the picture signal output of the Iconoscope.
These current impulses will appear in orderly sequence, as the electron
beam scans the area of the mosaic one horizontal line at a time from
top to bottom. It is in this order that the current impulses are trans-
mitted as television signals. Fig. 3 is a photograph of a repre-
sentative Iconoscope.

In the Iconoscope the charging process in any specific element of
of the mosaic continues for a time equal to the picture repetition in-

Aug., 1937]

RCA DEVELOPMENTS IN TELEVISION

125

terval; that is, until the beam, in the process, of scanning, returns to
that element. The electrical charge stored in the condenser increases
with this passage of time. The greater the electrical charge, the
greater will be the current impulse induced in the signal lead. This
storage principle makes the Iconoscope a very effective pick-up de-
vice for television.

The sensitivity of the Iconoscope is of great importance in picking
up a wide variety of scenes, both indoors and out, under practical
lighting conditions. This sensitivity at the present stage of develop-
ment is about the same as that of ordinary negative film. Research

VYAVfLfHiTH (ANSST/tOM VNIT3)

FIG. 4. Color-response characteristic of the Iconoscope.

in progress is disclosing methods by which it may be possible greatly
to increase the sensitivity.

The color-response of an Iconoscope depends upon the activation
schedule used in producing the mosaic and upon the composition of
the photosensitive material. The color-response characteristic may
be varied over a range comparable with that covered by photographic
emulsions available from motion picture work. The color-response
characteristic of a representative Iconoscope is shown in Fig. 4.

The Iconoscope and its associated optical parts correspond in the
RCA television system to the camera in motion pictures. This unit
of equipment is called the Iconoscope camera. Iconoscope cameras
having the same elements but differing in physical form are used for

126

R. R. BEAL

[J. S. M. P.

direct pick-up of indoor and outdoor scenes and for the transmissi<
of motion picture film material.

A photograph of an Iconoscope camera for use in indoor studic
is shown as Fig. 5. The camera may be moved about the studit
during a performance; it is raised and lowered by a motor-driver
mechanism; the usual provisions are made for following the motior

and action of the scene; it
silent in operation. The Icono-
scope mosaic is about 4 by
inches, or about six times
large as one 35-mm. motion
picture frame. Therefore the
Iconoscope camera lenses are of
greater focal length than those
employed in motion picture
cameras. Present Iconoscope
cameras are equipped with lenses
of 6.5- or 18-inch focal length.
Fig. 6 shows this camera, with
the housing raised. The picture
signals and the necessary power-
supply currents are carried by a
cable connecting the camera to
the system. A wide-band pre-
amplifier for amplifying the pic-
ture signal produced by the
Iconoscope is included in the
camera.

The picture signals generated
by the Iconoscope in the camera
are amplified and delivered to
the radio transmitter. These
signals are caused to modulate the carrier-wave of the transmitter
in a manner analogous to that employed in sound broadcasting.
The radio signal thus produced is picked up at the distant point by
the receiving antenna and delivered to the television receiver. Here
it is restored to its original form as a train of impulses. These
impulses are fed through amplifiers to the Kinescope, which trans-
forms them into a light-image upon the viewing screen.

The Kinescope is an evacuated glass envelope containing as the

FIG. 5. Iconoscope camera.

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION

127

FIG. 6. Iconoscope camera, with the housing raised.

128

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[J. S. M. P. E.

essential elements an electron gun and a luminescent screen. The
electron gun produces an electron beam similar to, but of greater

60 lines

120 lines

180 lines

240 lines

Enlargement

FIG. 7. Showing the improvement in detail with increasing numbers of
scanning lines.

current-carrying capacity, than the gun in the Iconoscope. Light is
produced when the electron beam bombards the luminescent screen.
The amount of light thus produced is proportional to the current

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION 129

in the beam. The electron beam is caused to scan the viewing
screen by appropriately applied electromagnetic fields.

The scanning beams in the Iconoscope and the Kinescope are ac-
:urately synchronized. The two beams are at corresponding points
jf the mosaic of the Iconoscope and of the luminescent screen of the
Kinescope at any instant. The brightness of a point on the lumines-
cent screen is proportional to the current in the bombarding beam.
This current is produced by voltages related to the picture signals
generated by the Iconoscope. These picture signals represent, by
electrical impulses, information concerning the brightness of each
picture element. Since the electron beams in the Iconoscope and
Kinescope are in exact synchronism, the brightness of any point on
the Kinescope screen will be a function of the brightness of the
corresponding point on the mosaic of the Iconoscope. Thus the
image projected upon the mosaic of the Iconoscope will be repro-
duced with exactness upon the viewing screen of the Kinescope.

The electron beams in the Iconoscope and the Kinescope are syn-
chronized by transmitting synchronizing impulses at the end of each
scanning line and at the end of each picture or frame. A synchro-
nizing amplifier in the receiver separates the synchronizing signals
from the composite signal by amplitude selection, separates horizon-
tal and vertical synchronizing signals from each other by frequency
selection, and delivers the impulses to the respective deflecting os-
cillators in proper amplitude and polarity for synchronization. The
requirement of accurate synchronization between the scanning beams
at the transmitting and receiving ends of the circuit is one of the im-
portant factors necessitating a uniform standard for all television
systems to be used in broadcasting services in this country.

As in motion pictures, the degree of technical perfection of the re-
produced image may be measured in part by the detail it contains.
To produce a system that will transmit and reproduce pictures of ac-
ceptable detail has presented one of the most severe problems in
television. The solution was found in the all-electronic system.

The amount of detail that can be transmitted by a television sys-
tem depends upon the number of picture elements resulting from
the scanning process. The number of picture elements depends
upon the number of lines by which a complete picture is scanned. A
picture element has a height equal to the distance between the cen-
ters of adjacent scanning lines; that is, the scanning-line pitch,
and a length 56 per cent greater than its height, for equal hori-

130

R. R. BEAL

[J. S. M. P. E.

zontal and vertical resolution in the picture. The number of picture
elements, and hence the amount of detail, increases with the number
of scanning lines. In a system that employs the Iconoscope and
other electronic devices, the number of scanning lines, hence the pic-
ture detail, may be greatly increased over that obtainable by earlier
devices and methods. The Iconoscope mosaic does not limit the
detail because many tiny photosensitive elements in the mosaic con-
tribute to a single picture element.

The detail that may be obtained by different numbers of scanning
lines is indicated in Fig. 7. These are synthetic representations de-

Photograph of a 441 -line television picture on the
viewing screen of the Kinescope.

veloped in the course of the studies of the subject. Pictures of less
than 60 lines were used in early experimental systems. The elec-
tronic system, embodying the Iconoscope and other electronic devices,
produces pictures of satisfactory detail with 441 scanning lines. This
amount of detail corresponds approximately to that obtained with
16-mm. motion picture film. A photograph of an actual 441-line
television picture is shown in Fig. 8. This is a photograph of an
image on the viewing screen of the Kinescope. The picture was
transmitted by the RCA system now under test in the New York
City area.

In television, as in motion pictures, two considerations are involved

Aug., 1937J . RCA DEVELOPMENTS IN TELEVISION 131

in determining the rate at which the scanning operation must be re-
peated. The rate of repetition must be great enough to give the ap-
pearance of reasonably continuous and natural motion in the repro-
duced scene, and must be great enough to minimize unsteadiness or
nicker in the reproduced picture. Continuity of motion is main-
tained with a repetition rate of 16 pictures or frames per second. At
least 48 frames per second are required, however, to minimize flicker
unless some artifice be employed. Motion pictures are projected at
the rate of 24 frames per second, and the artifice to reduce nicker
takes the form of an additional blade upon the shutter that interrupts
the light while the film is being pulled down from one frame to the
next. Thus, as far as flicker is concerned, the projection is, in effect,
at the rate of 48 frames per second.

Such an artifice is not applicable in television. Some other method
must be devised. Interlaced scanning is employed in the RCA sys-
tem. This provides satisfactory freedom from flicker. In interlaced
scanning, instead of scanning the picture in adjacent lines from top
to bottom, alternate lines covering the entire area of the picture are
first scanned, and then the beam returns and scans the omitted lines.
The entire picture is scanned 30 times per second, but the picture
area is covered in alternate lines 60 times per second.

Another requirement for consideration in television is the relation
that should exist between the frequency of the power supply to the
transmitter and receiver and the repetition rate. It is desirable that
the repetition rate be an integral divisor of the power-line frequency.
This is necessary to minimize certain synchronous interference effects,
which otherwise might be detrimental to the picture. The television
transmitter and receivers of the RCA field test system operate on a
60-cycle power supply. Hence a repetition rate of 30 frames per
second fulfills the requirements.

It should be noted that although the scanning beams of the Icono-
scope and the Kinescope must be in exact synchronism, it is not nec-
essary that the frequencies of the power supplies to the transmitter
and the receiver be synchronous, that is, interconnected, provided
they have the same nominal frequency and both systems are regulated
in frequency accurately enough for the operation of electric clocks.

The transmission electrically of high-definition images over a
single channel requires very wide frequency band apparatus and
circuits. This is occasioned by the rate at which information must
be transmitted concerning the brightness of a very large number of

132 R. R. BEAL \J. S. M. P. E.

picture elements. A 441-line picture with an aspect ratio of 4 to 3,
as transmitted by the RCA system, will contain 165,957 picture ele-
ments, for equal resolution horizontally and vertically. This is de-
rived from the product of the square of the number of scanning lines
and the aspect ratio divided by 1.56, the dimension of the picture
element in terms of the scanning line pitch.

When 30 pictures per second are scanned information must be
transmitted concerning the brightness of 30 times 165,957, or 4,987,-
710 picture elements each second. One cycle of the picture signal
provides such information for two picture elements; hence the total
frequency band required for transmitting a picture as above described
is about 2,500,000 cycles.

This is the width of the frequency band that must be amplified and
carried by the apparatus and circuits in the system. It is the fre-
quency band by which the carrier-wave of the radio transmitter must
be modulated. The total radio transmitting channel will be 5,000,-
000 cps. when the carrier is modulated by the picture signal. This
is equal to the combined widths of 500 sound broadcasting channels
of 10,000 cycles each.

Channels of such great width are not available in the frequency
spectrum now used for radio services. For this and other reasons
related to technical requirements, the ultra-high frequencies, or
ultra-short waves, are used for television. Frequencies above 30
megacycles (X < 10 meters) are employed. Ultra-short waves have
quasi-optical properties in propagation. The range over which satis-
factory high-definition television pictures may be reliably transmitted
by ultra-short waves is limited practically to the distance of the horizon
from the height at which the transmitting antenna is placed. Under
some abnormal conditions, pictures may be received over greater
distances for periods of very short duration, but primarily television
stations will serve local areas. The signals from the stations in these
local areas will be stable and will have about the same intensity dur-
ing the day and night hours, and during the seasons of the year.

Television networks for the simultaneous distribution of programs
originating at one point will consist of interconnected local stations.
The circuits interconnecting these stations must be capable of trans-
mitting the very wide frequency band required for high-definition
television. Existing circuits, either wire or radio, can not fulfill
this requirement. New facilities must be provided ; and while wide
frequency band circuits, either cable or radio, are feasible technically,

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION 133

to provide them for extensive, nation-wide networks become an
economic problem of magnitude.

The development of a high-definition television system has re-
quired technical advances over a broad front. Fundamental re-
search in an unexplored portion of the radio-frequency spectrum was
required to determine the laws of propagation of ultra-short waves
and to produce methods and devices by which they may be applied.
Entirely new methods and apparatus had to be produced for picking
up images and converting them into electrical impulses for transmis-
sion. New methods and devices were required for amplifying, trans-
mitting, and receiving the very wide frequency bands on ultra-short
waves. The fundamental character of the work and its extensiveness
constitute practically the development of a new art.

The technical advances made through a step-by-step program of
research in the laboratory, and through practical tests in the field,
have been incorporated in the television system RCA now has under
experimental test in the New York City area.

The equipment provided for this field test is installed under con-
ditions that closely correspond to the requirements of a television
broadcasting service. The field tests are comprehensive in scope.
They embrace studies of the functioning of the equipment under
field conditions; the collecting of engineering information and data
related to signal and noise levels within the service area; experiments
to develop program technic; and observations on receivers in the
field by technical personnel.

This system is now using standards of which the essentials are
441-lines per frame, a frame frequency of 30 per second, a field fre-
quency of 60 per second (interlaced), negative polarity of transmis-
sion, and a video-audio (picture-sound) carrier-frequency spacing of
3.25 megacycles. The picture signals are transmitted on a frequency
of 49.5, and the sound at a frequency of 52.75 megacycles.

The studios in which artists perform and from which motion pic-
ture film is transmitted are located in the RCA Building, Radio City
(New York). The radio transmitting equipment is installed in the
Empire State Building, and the transmitting antenna on top of the
building. The picture signals from the Radio City studios are sent
to the radio transmitter in the Empire State Building either by co-
axial cable or by ultra-short-wave radio relay. The accompanying
high-fidelity sound is carried over special cable circuits.

The terminal equipment at Radio City includes three Iconoscope

134

R. R. BEAL

[J. S. M. P.

FIG. 9. Radio City television studio.

FIG. 10. Studio control room.

lug., 1937] RCA DEVELOPMENTS IN TELEVISION

135

FIG. 11. Film projector equipment.

FIG. 12. Film studio control room.

136

R. R. BEAL

[J. S. M. P.

Cameras for direct pick-up in the artists' studio and two motioi
picture film projectors of special design, each with its Iconoscoi
camera. This equipment includes the video, or picture signal, am-
plifiers, and the deflecting and control apparatus for each Iconoscope
camera, the Kinescope monitors, the synchronizing generators, the
line amplifiers, and other associated apparatus.

FIG. 13. Synchronizing generator and video line amplifier
panels.

Television Studio. — The equipment in the Radio City television
studio is shown in Fig. 9 as it is used for a program transmission. In the
scene shown in the photograph, the Iconoscope cameras are employed
to pick up scenes to be transmitted in sequence by switching from
one camera to the other. The switching operation takes place in
the studio control room, which is located in an elevated position at
one end of the studio. The sound that accompanies the picture is
picked up by a standard velocity microphone equipped with a wind-
shield and attached to a boom.

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION 137

The studio is about 30 by 50 feet, with a ceiling height of about 18
feet. It is an NBC studio formerly used for sound broadcasting.
The studio is equipped with incandescent lamps of various types,
having a total power consumption of more than 50 kw. The lighting
equipment is flexible, to enable comprehensive studies of a variety of
effects in experimental programs. Rifles, floods, and focusing spots,
with ratings between 2 and 5 kw. each, are most numerous, although
there are several large units of special design. Key lighting and

FIG. 14. Inter-building ultra-short-wave radio relay
transmitter.

back-lighting units are suspended from the ceiling; modelling lights
are operated on the studio floor. The present sensitivity of the
Iconoscope requires an incident light-intensity upon a set of about
1000 to 2000 foot-candles.

Studio Control Room. — Adjoining the studio and at such an elevation
that the operating engineers have a clear view of the studio scene, is
the studio control room. This control room is shown in Fig. 10.
The sound and video signals from the studio are monitored in this
room. The scenes are picked up by the Iconoscope camera and re-
produced on the two monitoring Kinescopes shown at the left of the

R. R. BEAL

[J. S. M. P. E.

FIG. 15. Empire State Building control panel.

FIG. 16. Empire State Building video and audio transmitters.

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION 139

photograph. One monitor shows the scene 'being transmitted, and
the other the scene picked up by the second Iconoscope camera pre-
paratory to transmission. The operating position in the foreground
of the photograph controls the sound from the studio. The video
controls are at the opposite end of the control board. The racks of
equipment behind the engineers include the video amplifiers and the
synchronizing and control equipment associated with each Icono-
scope camera.

Film Studio. — Motion picture film material originates in a film studio
in another part of the National Broadcasting Company plant. This
studio consists of two rooms, in one of which are installed two special
35-mm. motion picture projectors and other supplementary equip-
ment, and in the other two Iconoscope cameras with video and
monitoring and control apparatus. The projectors are so designed
that standard 24-frame motion picture film is used to produce tele-
vision pictures at 30 frames per second. In these projectors a chang-
ing rate of intermittent drive is used for the picture portion of the
film and a constant 24-frame rate of feed for the sound portion. Pic-
tures from the projectors are focused on the mosaics of the Iconoscope
cameras located in the same control room beyond the partition sepa-
rating the two rooms. The film projector equipment is shown in
Fig. 11.

Film Studio Control Room. — A control room is associated with the
film projection room. A view of this room is shown in Fig. 12. The
equipment in the film studio control room includes two Iconoscope
cameras with their video voltage amplifiers and associated synchro-
nizing and control equipment, and audio equipment for the con-
trol of the sound from the film. The two Iconoscope cameras are
so mounted that they may be shifted from side to side for use with
either of the film projectors in the adjacent room.

Synchronizing Generator and Line Amplifier Equipment. — The panels
containing the electronic synchronizing generator equipment, and
the video line amplifiers that feed the video signal to the Empire
State Building are shown in Fig. 13. This equipment is installed in
the main equipment room of the National Broadcasting Company
plant.

Inter-Building Transmission. — The inter-building ultra-short-wave
radio relay transmitter (Fig. 14) is installed on the 10th floor of the
RCA Building. It operates on a frequency of 177 megacycles, and
has a channel width adequate to carry the full video frequency band.

140 R. R. BEAL [J. S. M. P. E.

Equipment is provided for monitoring the signal at this point. The
transmission distance between the two buildings is approximately
0.9 mile. The signal obtained at the Empire State Building is free
from noise, and pictures transferred by radio relay are as satisfactory
as those for which the coaxial cable is used.

Empire State Building Control Panel. — The coaxial cable and radio
relay channels, and the channel for the sound accompanying the pic-
ture from the studios in Radio City terminate at the Empire State
Building control board (Fig. 15). From left to right, the control
board consists of the sound channel panel, a video monitoring panel,
the radio relay receiver panel and battery and switching panels.
The video monitor may be switched either to the radio relay or the
coaxial cable channel.

Transmitters. — The video and audio transmitters installed in the
Empire State Building are shown in Fig. 16. The video and audio
transmitters are entirely separate, and are specially designed for
high-power operation on ultra-high frequencies. The modulator of
the video transmitter is capable of handling the wide side-bands re-
quired for the video frequencies. Both transmitters are coupled to
a common transmission line connected to the single antenna on top
of the building.

Antenna. — This antenna produces a horizontally polarized field with
a pattern essentially circular in the horizontal plane. The antenna
has a power gain in the horizontal plane of about 2.1, or 3.2 db.,
as measured with reference to a vertical dipole. The Empire State
Building, having a height of the order of 1250 feet, provides a loca-
tion from which a maximum transmitting range may be obtained.
The distance from the antenna to the horizon is approximately 43
miles. Fig. 17 shows a view of the Empire State Building transmit-
ting antenna.

Experimental Field Test Receivers. — The experimental field test re-
ceivers resemble in appearance a console broadcast receiver. Fig. 18
is a photograph of the type of receiver now in use. This re-
ceiver is of the superheterodyne type, and has a tuning range
of 40 to 84 megacycles. It receives the picture and the sound.
The Kinescope is mounted vertically and the television image
is viewed in the mirror mounted inside the cover of the cabinet.
Tuning is accomplished by a single knob controlling the radio-
frequency circuit and the single oscillator which heterodynes both
carriers to produce two intermediate frequencies.

Aug., 1937]

RCA DEVELOPMENTS IN TELEVISION

141

Of the seven knobs on the front of the receiver the center knob
tunes the picture and the accompanying sound. The three
knobs on the right, from top to bottom, are the sound volume
control, the treble tone control, and the bass tone control. The

three knobs on the left, from
top to bottom, are the picture
contrast control, the detail con-
trol, and the background bright-
ness control. These receivers
operate on the ordinary 110-
volt, 60-cycle power supply, and
draw about 350 watts of power.
These receivers have been
used to produce two sizes of
pictures. For the first few
months of the tests, the picture
size was 5l/t by 7Va inches. At
the present time most of the
receivers have Kinescopes that
produce pictures 7 l/z by 10
inches in size. Fig. 18 shows a
9-inch Kinescope that produces
a 5 l/t by 7 1/2-inch picture. A
Kinescope about 12 y2 inches in
diameter is required to produce a
7 l/z by 10-inch picture. The
shape of the picture, defined by
the aspect ratio 4 to 3, is the same as that used in motion picture
practice.

The brightness of the reproduced picture is such that it can be
viewed in a moderately lighted room. The color of the Kinescope
screen depends upon the composition of the fluorescent materials.
Many screen colors have been produced. At the present time a
slightly greenish yellow screen and a more nearly white screen are
being used. The present yellow screen used for the 7 x/2 by 10-
inch picture has a brightness in the highlights of about 4 foot-lam-
berts. This may be compared with the tentatively proposed stand-
ards of 7 to 14 foot-lamberts for the brightness of motion picture
theater screens.
The optimal viewing distance for a 441-line picture of the 7 l/z by

FIG. 17. Transmitting antenna on
tower of Empire State Building.

142

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[J. S. M. P. E.

10-inch size is of the order of three to four feet. At this distance the
line structure is not resolved by the eye. The screen angle or the
angle subtended by the picture at the eye is about 20 degrees. At a
viewing distance of 12 feet, the screen angle is about 5 degrees, which,
in general, is of the order of magnitude of the minimal acceptable
screen angle for motion pictures. The size and brightness of the 7l/z

FIG. 18. Experimental field test receiver.

by 10-inch picture of 441 lines appears to satisfy reasonably the re-
quirements for pictures to be viewed in the home by the average
family group

In connection with television program technic, it is too early to
predict accurately the technic that ultimately will develop in tele-
vision programming. It is clear to those who are closely associated
in the development of a system that although some parts of the pro-

Aug., 1937] RCA DEVELOPMENTS IN TELEVISION 143

gram technic may parallel the technics of the stage, motion pictures,
and sound broadcasting, it will be distinct from any of these. In
effect, a new art form must be created.

In general, television program material may fall under three prin-
cipal classifications. These are direct pick-ups from indoor studios
and other points, outdoor pick-ups, and motion picture film. Spon-
taneity eventually may be an important element in television pro-
gramming. The televising of outdoor events as they occur is en-
tirely feasible under the light conditions that prevail during fair
weather. Studio programs and motion picture film probably will
find liberal use in television programming, but here again the re-
quirements peculiar to television will affect the nature and composi-
tion of the material.

The field tests in the New York City area are contributing to fur-
ther technical advances. Pictures of 441 -scanning lines have been
transmitted and satisfactorily received within a service area having
a radius of 30 miles or more from the Empire State Building. Good
pictures are regularly received at one observing point in a suburban
home over a distance of 45 miles.

Much remains to be done. When it will be completed can not be
accurately predicted. The engineering information and data col-
lected and the experience gained from operating the system under
field conditions are pointing the way toward the realization ulti-
mately of a high-definition television broadcasting service.

This new service, just as have many new services in the past, will
supplement and not supplant the existing services or agencies rep-
resenting the older arts. The telephone did not supplant the tele-
graph; it supplemented it. Sound broadcasting did not supplant
the theater and the motion picture. On the contrary, it increased
public interest and appeal in them, and thereby contributed to their
advancement and financial profit. And so it will be with television.
When it is successfully accomplished, we shall have added another
service to the continually growing list. There will be some things
that television can do that previous arts can not do; a few things
that it can do better than they; but there will be many things that
they will continue to do that television can not do. We may there-
fore welcome the advent of a great new public service, which will
come not to displace but to augment our agencies of entertainment
and information, thereby making the world a more interesting place
in which to live.

TELEVISION FROM THE STANDPOINT OF THE
MOTION PICTURE PRODUCING INDUSTRY*

Summary. — This report supplements the report of May 15, 1936, of the Scientific
Committee of the Research Council of the Academy of Motion Picture Arts & Sciences.
Developments since the appearance of the first report are traced briefly, specific refer-
ence being made to the recent British experiment and other developments abroad, as
well as to the field-tests now being conducted in America.

The Research Council's first report on the status of television was
released on May 15, 1936. * This, the second announcement on the
subject, is therefore a review of a full year's progress in this field.

The members of the reporting committee are too well aware of both
the potentialities and uncertainties of technological research to claim
infallibility for such predictions as their task entails. It happens,
however, that only one of the forecasts contained in the 1936 report
requires, as yet, any essential modification. In every other particu-
lar the 1936 report is as valid now as when it was issued. To quote
from that report, it is still improbable that television will burst on an
unprepared motion picture industry; many millions of dollars must be
invested before nation-wide urban exploitation of television becomes
possible in the United States ; the start of such a development, fore-
cast for 1937-38, is confirmed; television service for rural areas is
still beyond the calculable future. The one change to which we would
call attention is that recent improvements in the design of electronic
projection devices give promise of a considerable enlargement of tele-
vision screen area, the realization of which would vastly accelerate the
evolution of television as a practical art.

THE BRITISH EXPERIMENT

It is legitimately claimed for the transmissions inaugurated from
the Alexandria Palace in London, on November 2, 1936, that they
constitute the first and only existing public television service. For
this achievement the British Broadcasting Company, the Marconi-
Electrical Musical Industries, the receiver manufacturers, and the

* Reprinted from Technical Bulletin (June 15/1937) of the Research Council
of the Academy of Motion Picture Arts & Sciences, Hollywood, Calif.

144

TELEVISION IN MOTION PICTURE INDUSTRY 145

other governmental and private interests involved deserve the credit
due to pioneers in a difficult field. Looked at realistically, however,
theirs is still an experiment, as is any enterprise in which more prob-
lems are raised than solved.

The accomplishments may be summed up as follows :

(1) Regular transmissions for two hours a day over a period of seven months,
using an all-electronic system with 405 lines and 50 pictures a second, interlaced.

(2) The sale of not over 1000 television receivers in a highly populous area
within, roughly, a 60-mile radius from the transmitter.

(3) The development of technic and operating organization, including multi-
camera pick-up, studio procedure, special effects, training of personnel, accumula-
tion of engineering data, etc.

(4) As a special event, the televising of the Coronation procession, under ad-
verse weather conditions, to some thousands of viewers.

Our correspondents in England agree, however, on the following
adverse conclusions:

(1) The received pictures, which are of the order of 71/2 by 10 inches, are too
small to afford more than scant entertainment value, even if other technical diffi-
culties, such as a consistent lack of definition in the longer shots, are overcome in
due course.

(2) The cost of the receivers, 60 and 80 pounds ($297 and $396 at the present
rate of exchange) makes television a toy of the well-to-do.

(3) The theatrical content of the video broadcasts has rarely risen above the
level of mediocrity.

In short, the picture is small, the cost high, the show poor, and the
patronage meager. Even allowing for the success of the Coronation
visual broadcast, we have to date an entertainment tour de force,
rather than a spontaneous growth in answer to a genuine public de-
mand. As for the economic question, it is no nearer solution than
when the experiment was inaugurated. It is argued that if larger
governmental subsidies can be secured, better shows will become
available, and eventually wide-spread public interest and participa-
tion can be enlisted. Perhaps so. In the United States a few thou-
sand radio amateurs listened to the Highbridge audio broadcasts in
1916; a few years later the number of broadcast listeners had risen
into the millions. In the case of British television it is too early to
draw conclusions. At the moment one can say only that such an
efflorescence is a hope rather than an early probability. By the end
of the year there should be signs of a healthy impetus from within, or
the enterprise will begin to have the appearance of that languishing
type that needs interminable injections of outside aid.

146 TELEVISION IN MOTION PICTURE INDUSTRY [J. S. M. P.

OTHER DEVELOPMENTS ABROAD

In Germany there is considerable television activity. Scenes froi
the Olympic Games were televised, but apparently the results wei
unimpressive. In France the forthcoming installation of a 30-kilo-
watt transmitter on the Eiffel Tower is announced. There are als
reports of Russian purchases of television equipment in the Unite
States.

AMERICAN DEVELOPMENTS

In the United States the active television interests have accepted
the Radio Manufacturers Association standard of 441 lines, a frame
frequency of 30 pictures a second, a field frequency of 60 pictures a
second, interlaced, and an aspect ratio of 4:3, the same as in motion
pictures. These are the present characteristics of the test trans-
missions by the National Broadcasting Company from the Empire
State Tower in New York, which are the nearest American equivalent
to the British operations reviewed above. (The former, however, is
not a public service; the receivers, of which there are over one hun-
dred, being in the hands of RCA executives and engineers who report
confidentially on the results.) The shows originate in a special
studio in the RCA Building and are relayed to the transmitter over a
coaxial cable and a radio link between the two buildings, whose air-
line separation is under one mile. The power of the transmitter, 7.5
kilowatts, is sufficient to lay down a satisfactory signal on the optical
horizon, which is some 43 miles from the top of the 1250-foot tower.

The size of the received pictures is about the same as in the British
case: 7l/z by 10 inches. Such a picture is afforded by a 12l/2-inch
cathode-ray tube, a size readily manufactured in the present state of
the art.

This experimental service has been in operation for about eleven
months, with an interval to permit changing the transmitter from the
earlier 343-line standard to 441 lines, and some briefer interruptions.
A mass of data on the technic of televising, electrical interference con-
ditions, signal distribution, etc., has been and is being collected. Pa-
pers describing the technical aspects of the research are presented peri-
odically before the Society of Motion Picture Engineers, the Institute
of Radio Engineers, and other recognized bodies. In connection
with one of the most recent of these papers there was a demonstration
on a scale as large as 10 by 8 feet, using optical projection from a Kine-
scope equipped with a suitable lens system, with, it is said, impressive

Aug., 1937] TELEVISION IN MOTION PICTURE INDUSTRY 147

results. (Similar experiments have been carried on in Germany, but
there it was reported that the optical quality of the larger pictures
was unsatisfactory.)

Occasional television programs are transmitted from a Philco
station in Philadelphia, and others. The Columbia Broadcasting
System has announced its intention of installing a television trans-
mitter on the Chrysler Tower in New York.

GENERAL CONSIDERATIONS]

Both here and abroad, systematic engineering progress is being
made in the development of high-definition television. The situation
has reached a point where it warrants careful observation and analy-
sis. Just as the physical equipment required can not be brought
into existence quickly, it is impossible to acquire a background in a
field as complex as television overnight, and study well in advance is
a prerequisite of wise and economical planning. The time is not far
off when those engaged in motion picture production, and others
whose interests are likely to be affected by the evolution of this new
field, will do well to acquire as much familiarity as possible with its
characteristics and methods.

We recur to the question of picture size. As soon as larger pictures
are available with the requisite photographic quality, television
may be expected to gain marked impetus, and commercial appli-
cation in the larger urban centers will not be long delayed. The
lesson to be derived from the British experience to date may be that
when those in a position to gauge entertainment value advise that a
given picture size is inadequate for successful commercial application
no purpose is served by trying it out on the public. The likelihood of
a favorable verdict does not increase with the size of the jury. For
the United States it is to be hoped that no attempt will be made to commer-
cialize home television until a picture equivalent in definition to the best
home-movie projection, and not smaller than 24 by 18 inches, can be
furnished with routine reliability. The most important interests in the
domestic field appear to be committed to some such prudent policy.

THE SITUATION IN LOS ANGELES

New York and Los Angeles together constitute the principal reser-
voirs of movie, radio, and television talent in this country. It may be
expected, therefore, that when the problems of providing television
service for the New York area are well on the way to solution, say, in

148 TELEVISION IN MOTION PICTURE INDUSTRY

1938 or early 1939, the next major urban area selected for television
coverage will be that of Los Angeles. The topographical and physical
conditions in the two regions are quite different, and, it would appear,
are on the whole more favorable in the West.

In New York the land elevations are relatively low, no point in any
of the five boroughs, excepting Staten Island, being as high as 300 feet
above sea level. To secure short-wave coverage, therefore, it is neces-
sary to radiate from high buildings, of which there is no scarcity.
However, the mass of steel structures on Manhattan Island of neces-
sity casts radio shadows that complicate the problem of television dis-
tribution.

Los Angeles, in contrast, is a city of low structures, but natural
elevations provide numerous sites from which television service could
be effectively provided. Cahuenga Peak, for example, with an alti-
tude of 1825 feet, affords an eminence about 50 per cent again as
high as the Empire State Tower, commanding the San Fernando Valley
to the north, the greater part of Los Angeles to the south and east,
and the beach cities to the west. Topographically, as well as from
the aspect of talent availability and entertainment facilities, Los
Angeles is a favorable site for a television center.

FUTURE REPORTS

In view of the progress being made in television, this Committee
feels it advisable to report its findings semi-annually hereafter, and is
scheduling its work accordingly. The next report will thus be issued
in January, 1938.

CARL DREHER, Chairman

GORDON CHAMBERS BARTON KREUZER WESLEY C. MILLER

L. E. CLARK GORDEN S. MITCHELL HOLLIS MOYSE

J. G. FRAYNE WILLIAM MUELLER

REFERENCE

1 "Television from the Standpoint of the Motion Picture Industry," Technical
Bulletin (May 18, 1936), Academy of Motion Picture Arts & Sciences; reprinted
/. Soc. Mot. Pict. Eng., XXVI (July, 1936), No. 1, p. 74.

REPORT OF THE STANDARDS COMMITTEE*

Summary. — Revised drawings for most of the standards, except those on sound
sprockets, have been prepared and are to appear in a forthcoming issue of the Journal.

There have been no fundamental changes except with regard to the sound-film. For
35-mm. film, the dimensions of the sound-track have been changed; and for 16-mm.
sound-film, similar changes have been made and the distance between the picture and
the corresponding sound has been changed to 26 frames.

Inasmuch as the revision of the standards drawings being prepared
by the Committe will be published in an early issue of the JOURNAL,
they will not be given at this time. Most of the changes have to do
solely with tolerances and with improved forms for showing the
essential dimensions.

New Drawings. — The most important actual change recommended
is an increase in the width of the variable-width sound record on
35-mm. film from 0.071 inch to 0.076 inch. The latter value is actu-
ally in use now, and was introduced to make room for the double
track for the push-pull recording system. This change involves also
a change in the sound-track dimensions for 16-mm. film to allow for
reduction printing. The width of the sound record is increased from
0.060 inch to 0.064 inch. The width of the printed area for the
variable-width sound-track has been reduced, however, from 0.096 to
0.085 inch so that the printed area for both types of sound records
is the same.

Screen Brightness. — In accordance with the recommendation of the
Projection Screen Brightness Committee and its endorsement by the
Projection Practice Committee, the Standards Committee is propos-
ing to adopt as recommended practice a standard screen brightness
of not less than 7 or more than 14 foot-lamberts. There have been
some good arguments against this recommendation, and further
comments will be welcomed before the final adoption of this recom-
mendation.

Standard Densities. — After investigation by the Sub-Committee to
determine the possibility of standard densities for standardizing den-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
20, 1937.

149

150

REPORT OF STANDARDS COMMITTEE

sitometers, the recommendation has been approved by the Standards
Committee that strips of photographic film standardized by reference
to an integrating-sphere densitometer be used as reference standards.
In spite of the fact that these densities are not permanent, it is be-
lieved that they are as permanent as any other densities likely to be
obtained, and have the further advantage of offering approximately
the same degree of light-scattering as the photographic film with
which they are to be compared.

16- Mm. Spools for Projection Reels. — In spite of the fact that in
Europe it appears likely that a standard reel for educational sub-
standard film will be adopted with square holes on each side, the
Standards Committee here has voted to adopt the recommendation
of the Committee on Non -Theatrical Equipment that all such reels
be built with a round hole on one side and a square hole on the other.

P. ARNOLD
M. C. BATSEL
F. C. BADGLEY
L. N. BUSCH
A. CHORINE
A. COTTET
L. DE FEO
A. C. DOWNES

J. A. DUBRAY

P. H. EVANS

E. K. CARVER, Chairman
R. E. FARNHAM
C. L. FARRAND
G. FRIEDL, JR.
H. GRIFFIN
A. C. HARDY

R. C. HUBBARD

E. HUSE
C. L. LOOTENS
K. F. MORGAN
T. NAGASE

N. F. OAKLEY
G. F. RACKETT
W. B. RAYTON
C. N. REIFSTECK
H. RUBIN

0. SANDVIK
H. B. SANTEE
J. L. SPENCE

J. VAN BREUKELEN

1. D. WRATTEN

REPORT OF THE WESTERN MUSEUM COMMITTEE*

Summary. — A brief account of new accessions to the SMPE motion picture exhibit
at the Los Angeles Museum, and a description of two new galleries added to the dis-
play facilities.

The Historical Committee has been active in collecting relics,
memorabilia, and data concerning the past as well as the present of
the industry and its personalities, so that complete records may be
preserved in the SMPE exhibit at the Los Angeles Museum.

The historical exhibit and files have been of considerable help to
authors preparing books on cinematic subjects, a number of authors
having used the museum data in some of their publications.

A second gallery has recently been added to increase the display
facilities at the Los Angeles Museum. In it are being exhibited
paraphernalia and material illustrating many of the advances of
cinematic science. The gallery serves a two-fold purpose: first, as
the "Science of Motion Picture Production Gallery," it tends to give
the visitors some knowledge of the functions of various studio de-
partments in film production; second, it encourages engineers and
inventors to make available apparatus and documents of their
achievements for preservation. It is particularly desirable that
exhibits representative of all phases of motion picture production be
submitted. The gallery already includes displays illustrating many
phases of motion picture making. One such exhibit covers the proc-
ess of designing a set. In the latter display, chronologically ar-
ranged, are material illustrating the various steps taken in designing a
setting from a manuscript, drawings ranging from the conceptual
sketches of the art department to those of the final model, and photo-
graphs of the completed set.

Another exhibit includes equipment showing in a popular manner
how sound is recorded. In this display are records made of soft wax,
light-valves, tubes used in sound systems, paraphernalia for special
sound effects, and other devices, as well as some historical relics.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
24, 1937.

151

152 WESTERN MUSEUM COMMITTEE REPORT [J. S. M. P. E.

Illumination and set lighting are demonstrated by devices and photo-
graphs. The application of color to motion picture film is illustrated
by drawings and objective material. A prop department, recon-
structed to represent a cross-section of a typical movie-prop depart-
ment, has been built in one section of the gallery. Noted props and
materials used for dressing sets of outstanding films make up the
prop display.

In addition to the technical material and in order to make the
gallery as comprehensive as possible, exhibits showing how films are
publicized and campaigned are also included.

Space is available in the gallery for displaying all significant ma-
terial. Material may be submitted on a temporary loan basis, al-
though outright presentation is preferred so that the records and
equipment may be regarded as permanent.

In the historical gallery the work of bringing together the memor-
abilia and relics has gone forward, and much new material has been
added during the past year. An animated cartoon display using
original drawings and score-sheets from cartoon films made by Walt
Disney, the Harmon-Ising Co., and Walter Lantz illustrates the film-
ing and departmental procedure in production. A case of original
background paintings and drawings of cartoon characters from the
representative producers of today has been added to the display. Ma-
terial from cartoon films that have won awards and attracted much
public attention has also been acquired and is on display.

Mr. J. R. Bray has made available a group of photographic enlarge-
ments from his first cartoon, The Artist's Dream, released on June
12, 1913, from which the entertainment possibilities of the cartoon
film first became apparent, and the popularity of this form of cine-
matic medium first became evident. There were, of course, earlier
cartoons, such as those made by Vitagraph as early as 1906.

Many catalogues of manufacturers of motion picture equipment
have been acquired, dating back as far as 1898. This kind of material
is valuable to research students who wish to investigate the progress
of the industry.

A number of relics portraying the pioneer attempts to produce
animated pictures have been obtained. One such relic is a motion
picture of twelve exposures, with a single pin-hole between each frame
instead of perforations for advancing the film. The pin-hole perfora-
tions are reinforced. Each frame is about-3V2 inches square. It was
made by E. H. Amet on a piece of kodak roll film, and judging from

Aug., 1937] WESTERN MUSEUM COMMITTEE REPORT

153

the general texture of the celluloid and from, comparisons with other
films, the 40-inch motion picture was made about 1894-95. Many
other exhibits have been received, including early cameras, projectors,
and other materials.

The Committee has been bringing together biographical records for
publication and for future reference, and anyone having documents or
records of pioneering activities is invited to submit the material
for consideration.

To help preserve the relics of the motion picture industry, the
membership of the Society is invited to send material and documents
to the Los Angeles Museum for preservation, for depositing or on either
a loan or gift basis. Cards crediting the donor with the gift or loan,
and outlining the history of the piece are attached to the exhibits in
the display gallery.

J. E. ABBOTT
T. ARMAT

E. THEISEN, Chairman
G. A. CHAMBERS
W. CLARK

G. E. MATTHEWS
T. RAMSAYE

REPORT OF THE PAPERS COMMITTEE*

Summary.— A brief account of the plan followed by the Committee in constructing
and arranging Convention programs.

A year ago this Committee initiated the plan of publishing in the
JOURNAL abstracts of the papers and Committee reports to be pre-
sented at the Semi-Annual Conventions. This plan has been fol-
lowed for three consecutive meetings, the material being published
each time in the issue of the JOURNAL appearing several weeks prior
to the Convention. Abstracts of approximately eighty-five per
cent of the papers and reports for these three meetings have been
published, and it is believed that the publication of these abstracts
has aroused greater interest in the meetings, helped to increase the
attendance, and facilitated the discussions.

In our April, 1936, report a proposal was made that the program of
the next Convention should be prepared as follows: (a) publication
of a request for papers in the issue of the JOURNAL published five
months before the meeting and in each succeeding number prior to
the meeting; (b) personal solicitation of papers on subjects of current
interest; (c) assignment of preferred positions, with ample time for
presentation and discussion, to the best papers submitted up to
approximately five weeks before the meeting; (d) balancing the re-
mainder of the program by adding papers as submitted up to about
three weeks before the meeting. An attempt was made also to obtain
a manuscript of each paper before it was read at the Convention.

A fair response to this plan was realized, but the number of manu-
scripts turned in by the date specified was not as great as had been
expected. The bulk of the preliminary program material was ob-
tained finally by urgent solicitation during the last week before it had
to be released for printing. Manuscripts were obtained, however, for
90 per cent of the papers.

At the open forum, which was held at the Rochester Convention
on Friday afternoon (Oct. 15, 1936), comment was made that our

* Presented at the Spring, 1937, Convention at Hollywood, Calif. ; received May
13, 1937.
154

REPORT OF PAPERS COMMITTEE 155

programs were too crowded with papers, and that insufficient time
was allowed for discussion. It is very difficult to know exactly how
much time to assign to a paper, because the ability of authors to
present their papers in a condensed but clear manner varies consid-
erably. Each author has been urged to rehearse his presentation,
but we fear that very few authors do so.

The Committee well realizes the importance of intelligent dis-
cussion, but we wish to point out to the membership that, in addition
to a Convention program, the Society also publishes a monthly
JOURNAL. The papers read at the Semi-Annual Conventions com-
prise 95 per cent of the material for this JOURNAL. We have nearly
1400 members distributed throughout the world. Of the 1400 it
must be remembered that perhaps 1000 never get to our meetings.
Those members depend upon the JOURNAL as their source of informa-
tion, and, in fairness to them, it is very important that the present
size of the JOURNAL be maintained.

The editorial office has been faced twice during the past year with
an acute shortage of material for several issues of the JOURNAL, which
has been alleviated only by vigorous efforts by this Committee and
the Board of Editors. A healthier situation would be to have on
hand more material than is required, from which the best could be
selected for publication.

Although the number of papers submitted for publication only
(not read at the Convention) has increased slightly in recent years,
the stimulus of attendance at a Convention is apparently necessary
to get the majority of authors to write papers for the JOURNAL.

It is of interest to note that 32 of the 35 papers read at the 1936
Spring Meeting, and 30 of the 34 papers read at the 1936 Fall Con-
vention, have been published. These figures indicate, however, that
very little material was on hand on May 1, 1937, for the July, 1937,
issue, and how necessary it is that manuscripts for each meeting be
turned in to the Committee before each meeting.

To remedy this situation and alleviate somewhat this shortage of
material, the Papers Committee urgently requested in January that
the Board of Governors approve a five-day Convention in May, 1937.
This was done, and with the cooperation of a special local section of
the Committee we have been able to arrange a well balanced program.

For discussion of the technical papers, 25 per cent of the total time
allotted is intended for discussion, and 50 per cent of the total time
for apparatus papers. It is believed that, with the full cooperation

156

REPORT OF PAPERS COMMITTEE

of the authors and of those who take part in the discussions, the pro-
gram will go forward as scheduled.

C. N. BATSEL
L. N. BUSCH
O. O. CECCARINI
A. A. COOK
L. J. DIDIEE

G. E. MATTHEWS, Cltairman
C. FLANNAGAN
M. E. GILLETTE
E. W. KELLOGG
R. F. MITCHELL
W. A. MUELLER
E. C. RICHARDSON

T. E. SHEA

P. R. VON SCHROTT

H. C. SILENT
H. G. TASKER
I. D. WRATTEN

C. N. BATSEL
O. O. CECCARINI

Local Papers Committee

W. A. MUELLER, Chairman
L. A. AICHOLTZ, Secretary
E. C. RICHARDSON

H. C. SILENT
H. G. TASKER

A NEW VIEWPOINT ON THE LIGHTING OF MOTION

PICTURES*

G. GAUDIO**

Summary. — The lighting of motion pictures is discussed with relation to a new
lechnic developed by the author and employed in several recent productions, notably
"Anthony Adverse" and "The Life of Emile Zola."

The use of artificial lighting for motion picture scenes originated with attempts to
imitate the flat overall illumination produced by daylight on the early "daylight"
stages. When the concepts of modelling and effect lighting were introduced, they
were regarded merely as adjuncts to an overall flat general lighting. They have, in
the main, so continued until today, despite the great advances made in optics and
sensitive materials.

The author holds that under modern conditions, this lechnic is faulty. He has
therefore dispensed with the so-called "general lighting," and has for some time done
all his lighting with various types of spotlighting units. This enables him to light
more precisely; to accommodate his effects and his equipment to the physical require-
ments of modern production technic; and to achieve more natural effects upon the
screen.

The lighting of motion pictures is an outstanding example of the
way the creative artists who work actually on the sets are linked to
the creative engineers who work behind the scenes developing im-
proved equipment and materials for their use. Each improvement in
tools or materials makes it possible to evolve new and better tech-
nics for using them.

Within the past few years two such improvements have been
brought out. The film manufacturers have provided faster, more
delicately sensitive emulsions. The lamp manufacturers have pro-
duced more precisely controllable lighting units.

The result, in the writer's case, at least, has been the development
of a new and more precise method of lighting, which has been proved
in actual use on such productions as Anthony Adverse and The Life of
Emile Zola.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 24, 1937.

** Warner Bros. -First National Studios, Burbank, Calif.

157

158

G. GAUDIO

[J. S. M. P. E.

In order to understand any new development, it is always a good
idea to glance backward to see what has gone before. Often it makes
it easier to see why things evolve as they do. The earliest motion
pictures were all illuminated by natural light, whether the scene
represented an exterior or an interior. The reason for that was
simple: thirty or forty years ago even the best emulsions were
painfully slow; and lenses, judged by present-day standards, were
even slower. An aperture of //4.5 was regarded as the acme of speed;

FIG. 1. Scene from The Story of Entile Zola, showing the effect of spotlight-
ing through the skylight.

many cine* lenses worked at still smaller openings. Emulsions had
an H&D speed of less than 400, compared to present-day speeds of
1000. At the same time, cin£ exposures had to be made at an average
shutter-speed of Veo second or less.

Clearly, the sun was the only light-source of sufficient intensity to
make an exposure possible under such conditions.

It is true that some fairly powerful artificial light-sources existed
in those days, but using them in quantities sufficient to illuminate
even a tiny set was generally economically impossible for the early
producers, many of whom had virtually exhausted their capital in
buying or leasing a single camera and a scant supply of film.

Aug., 1937] LIGHTING OF MOTION PICTURES 159

So, for many years, motion picture scenes — exterior and interior
alike — were illuminated solely by sunlight. Some of the earliest
studios were simply the flat roofs of office buildings, with the sets
made of "flats" of painted canvas hung against the walls of adjoining,
higher buildings.

Later, as the film business prospered, studios were erected especially
for motion picture making. These were at first simply unroofed, un-
walled floors over which intricate systems of muslin curtains were

FIG. 2. Scene from The Story of Emile Zola, in which the set and charac-
ters are lighted almost entirely by spots.

stretched to diffuse the light. Later, glass-paned roofs and walls
were added to make the stages weather-proof. In consequence of
these conditions, the ideal lighting of the period was simply a flat,
even flood of light throughout the set. No attempts at modelling or
light-effects were possible, or even thought of.

Inevitably, as the business grew further, the fact that a company
could not work when the weather was bad became an economic hin-
drance. This was specially noticeable in the East, where production
was then centered, and where the weather can be cloudy and stormy
for days and weeks at a time. The answer to that was the intro-

160 G. GAUDIO [J. s. M. P. E.

duction of artificial lighting. Perhaps the studios could not afford
the new expense; but they could afford still less to let their releases
wait on the weather.

So the earliest use of artificial lighting was nothing more than a
matter of substituting a powerful artificial illuminant for the sun.
There were two principal types of lamps used at that time. There
were the "Aristo" arc lamps, adapted probably from street-lighting
service, and the Cooper-Hewitt mercury-vapor tubes. Whichever
type was used, the lamps were permanently fixed in place, being
usually swung on chains or rigid supports from the roof of the stage.
In many installations the lamps represented fixed units, and the sets
were built beneath to conform to the lighting. Ultimately, similar
floodlighting units, both arc and vapor-tube, were mounted on stands
and used on the floor beside the camera, to light the sets from the
front.

The result, of course, was simply a flat, fairly even flood of light
throughout the set. No modelling was thought of ; very little would
have been possible, anyway, since only floodlights were available.

Moreover, in many instances any departure from a fixed scheme of
flat lighting was frowned upon. Back in 1913 or 1914, when I was
photographing The House of Discord, with Blanche Sweet, Lionel
Barrymore, and Marshall Neilan, at the old Biograph Studio on
175th Street, in New York, I very nearly lost my job because I tried
to reproduce the glow cast from a fireplace. As late as 1915 or 1916
my fellow-cameraman David Abel, who is responsible for the dis-
tinguished photography of the Fred Astaire successes, was dismissed
by a studio for the unheard-of crime of shining a spotlight through a
window to create the effect of a beam of sunlight!

However, the demand for such natural effects, and the then newly
discovered value of back-lighting to separate the actors from their
backgrounds, ultimately brought about the introduction of spot-
lighting equipment. The condensing-lens spotlight was borrowed
from the stage. Later, as sets grew larger and more intense beams
were needed, the mirror spotlight was borrowed from searchlighting
service. With these tools at hand, lighting took on a new aspect. As
time went on, it was learned that lighting could make or mar the ap-
pearance of the players; that it could model their forms and faces;
and that it could give an illusion of depth and solidity to the setting.

Still, be it understood, this use of lighting was merely in addition to
a flat overall lighting which provides the illumination for the ex-

Aug., 1937] LIGHTING OF MOTION PICTURES 161

posure. Wherever sunlight alone could serve, it was made to do so.
This was especially true here in California, where the climate was the
original attraction to the industry. Nevertheless, even here the use
of sunlight for illuminating interior scenes slowly but surely gave way
to the use of artificial light. Yet it was not until we were well into
the 1920's that the glass walls of the last "daylight" stages were
opaqued out, and only within the last two years did the last open
stage in use (at the Chaplin studio) make way for a closed sound stage.

During those years, successive improvements were made in film and
lenses, as well as in the usable apertures of camera shutters. Film
speeds increased to 600, 800, and 1000, H&D; lens speeds increased
to//3.5, f/2.7, and beyond. Shutter apertures widened from 90 and
120 degrees to 170 or 180. Such advances made it possible to use
less light and to alter negative development procedure to give a
softer, more pleasing negative. Each advance made corresponding
changes in the lighting technic.

About ten years ago came two sudden changes, almost together,
which altered the entire conception of lighting. These were the
introduction of panchromatic film and the coming of sound. Pan-
chromatic film had been available for some time before any of us
in the studios dared to try it. It is one thing to try a new product
for oneself, and quite another thing to risk an employer's investment
of hundreds of thousands of dollars on something so radically different
as was panchromatic film. But one by one we tried the new film, and
were convinced. I believe I used it on the first big production to be
photographed entirely on "pan" when I photographed Hell's Angels.

With panchromatic film, the softer, yellower light of the incan-
descent or Mazda type of lamp was more satisfactory than the hard ,
blue light of the arc. Most cinematographers rather preferred to use
the arcs, however, for they were more accustomed to them.

Then came sound. As soon as the microphone joined the troupe,
the early arcs had to go, because the sizzling noise made by them
was recorded on the film. Whether we wanted to or not, we had to
change to the quieter Mazdas.

Personally, I think I was lucky in that respect, for I had had the
privilege of making many of the Mazda lighting tests filmed in the
Hollywood-Roosevelt Hotel by the American Society of Cinema-
tographers, the Academy of Motion Picture Arts & Sciences, and the
Producers' Association. Changing to Mazdas on production was
not such a problem.

162 G. GAUDIO [J. s. M. p.

Actually, the change to Mazda lighting did not change thinj
fundamentally. The basic principles of lighting remained unchanj
Where formerly we had had arc floodlights, condensing-lens ai
spotlights, and mirror-arc spotlights, with some mercury-vapor tut
we now had incandescent floodlights, incandescent condensing-ler
spotlights, incandescent mirror spotlights, and incandescent overhe
floodlighting strip units. Once we knew how they and the fih
worked together, we could and did use them almost exactly as
had used their arc counterparts.

Meanwhile, two new factors appeared. Emulsions grew steadily
more and more sensitive, progressing through Type // panchromatic
through Supersensitive to today's Super-^T. And the directors dis
covered that the slower-paced talkie could be speeded up by having
the camera move about the set.

Inevitably, these developments influenced lighting. As film
came faster, it became possible to use lower levels of illuminatioi
When that happened, we discovered that it was necessary to contr
our lighting with greater precision. Uncontrolled beams of spille
light straying from the spotlighting units, which formerly had beet
too faint to make any impression upon the film, now picked up em-
barrassingly.

With the modern directorial technic, the camera, instead of beii
statically set up to photograph a fixed combination of lighting anc
action, moves about the set continually. Every inch it move
changes its relation to the lighting. Consequently a set has to
lighted so as to appear right, not merely in relation to one viewpoint
but to perhaps a dozen viewpoints.

The first approach to these problems, and one still used by soi
cinematographers, is to flatten the lighting as much as possible, anc
get a good, conservative general illumination, with as much modellii
as they feel is safe. That, however, often tends to involve the use
more light than is necessary, and complicates the lighting set-uj
It sometimes, too, requires the use of a lot of floor units, which make
the manipulation of the camera-carriage or boom more difficult.

This method, to me, is attacking the problem wrongly. It cer-
tainly does not allow us to make full use of the materials and technics
at hand. We have camera equipment that can travel all over the
set, unless impeded by a maze of lamps and lamp-cables. We have
a film that is so sensitive that we can use less light than ever before.
We have spotlighting units, like the new Solarspots, which project

Aug., 1937] LIGHTING OF MOTION PICTURES 163

the light more efficiently than anything with which we previously had
to work.

Why not make use of these advantages?

During the past year, this thought kept returning to my mind with
every scene I photographed. I experimented a bit more on each
succeeding picture until the technic used in Anthony Adverse was
fully developed.

It might be termed "precision lighting," because it is achieved
almost exclusively with precision lighting tools — spotlights. General
floodlighting, formerly used to assure a safe exposure-level of illu-
mination over all, is no longer needed or used. Instead, every detail
of both actors and set is illuminated by light-beams projected from
spotlights. There is no difference in the amount of light used, but
since every beam can be controlled precisely, there is a tremendous
improvement in the result on the screen.

Our normal concept of light is that it comes from above. Outdoors
even on a cloudy day, the light comes from the sky above us. Indoors
in the daytime, the light comes through the windows on a downward
slant; at night, most of our artificial lighting fixtures cast their rays
from a position generally above eye level. Why, then, in photo-
graphing a motion picture should we play our light on sets and actors
from any angle but above ?

It is true that lighting actors from above may cause shadows under
the eyebrows, chins, and so on. At least it would if we illuminated
the actors with but one concentrated beam. But in practice, we
almost never light a player so crudely. No matter what effect we
may be seeking, or what method of lighting we use, we light each
actor with several beams, of various intensities, spread, and diffusion,
and from several different directions. With all these beams we can
either wipe the shadows completely out, or turn them to advantage
in giving naturally modelled, three-dimensional effects.

Therefore, if any of you should visit a set where I am making a
picture, you would find that all my lighting units are spotlights, ar-
ranged on the lamp-rails above the set. Only in rare instances is it
necessary to use lamps on the floor. Sometimes there may be an
inaccessible corner of a set that can be illuminated only by a beam
projected from a lamp placed upon the floor; sometimes, also, in
making close-ups it will be more convenient to use a lamp or two on
the floor for front-lighting. But normally there will not be a single
unit of any kind on the floor. All the lighting is done with spot-

164

G. GAUDIO

[J. S. M. P.

lighting units — condensing-lens spotlights, mirror spotlights, and the
new Fresnel-lensed Solarspots.

There is another precision lighting tool that plays a big part in m]
lighting — the dimmer. When the electricians are getting the lamj
ready for rigging a set for me, they know that floodlighting equipment
will not be needed, but rather four to half a dozen or more smal
dimmers. I can then re-balance the lighting by bringing this unit
up or that one down, as the players or the camera move about the
set.

For instance, in Zola there is a scene played in an artist's studic
overlooking Paris. The far wall of the set consisted almost entirely
of broad windows and skylights. Now in real life, in such a room,
all the illumination would come from the windows, so I illuminated
my set in that manner. A series of spotlights on the lamp-rail above
the set projected beams down through the skylight and the window.
From the opposite rail, just enough diffused light was projected to
relieve the shadows caused by this strong key -lighting, and to prevent
the scene from being an absolute silhouette. These two angles of
light were carefully balanced to produce a natural effect.

This lighting balance was not, however, enough to show up an
actor's facial expression if that was important, as it was in one part
of the scene. Here is where the dimmers played their part. For
good part of the scene, Muni played with his back to the camera,
looking out through the windows. Thus far, the lighting was satis-
factory. But a little later he had to turn and face the camera, to speak
an important line to a friend inside the room. The lighting balance
was no longer dramatically correct, for while the semi-silhouette
effect was precisely what the eye would actually see in such a room,
there was not enough front-light to show clearly the facial expressions.
If a big dimmer had been used to raise the intensity of all the front-
light, the effect would have been unnatural. So I used a smaller
dimmer, wired into the circuits of only the lamps focused upon the
one player. Normally, the lamps might be turned very low, or even
completely out. As Muni started to turn, the dimmer was slowly
operated to bring the intensity of the lamps up to the correct level.
When he turned away again, the lamps were dimmed again. Often
there are four or five dimmers on a set, each coupled to but one or
two spotlights, and the electricians will work the dimmers up and
down as the action requires. Sometimes a simple scene may have a
dozen dimmer changes.

Aug., 1937] LIGHTING OF MOTION PICTURES 165

There are a number of ways of building lighting. Some begin with
a general flood of flat, overall illumination sufficient to assure a safe
minimum exposure-level. Others key the lighting plan to the high-
lights, often counting on spilled light to illuminate the shadows satis-
factorily, and filling in with diffused spotlights and floodlights when
additional general illumination may be needed.

The writer's method is to begin by planning for the shadow -areas,
and build them up to the desired level with spotlight-beams. And
here is an important fact : in nature there is normally no such thing
as an opaque shadow. Even the darkest shadows ordinarily en-
countered reflect a little light, so that at least a suggestion of some-
thing can be seen. We may not penetrate the shadow enough to
make out all the details, but we can almost always get an idea of what
is in the shadow.

In photography, things are different. If a shadow does not reflect
enough light to make some sort of exposure on the film, the picture
will show merely an opaque, jet-black emptiness where the shadow
is. On the other hand, if we throw too much light into the area, there
is simply no shadow at all.

That is why I begin with lighting the shadows. Since our most
modern lighting units emit little or no spilled light, rays from them
are not to be counted upon to keep the shadows transparent. Ac-
cordingly each shadow is illuminated to the exact level required in the
completed lighting. From the shadows it is a natural progression up
through the middle tones to the highlights.

There is a natural focal highlight in every scene, which almost al-
ways coincides with the center of interest of the scene. Just as an
art director, when making a perspective drawing of a set, starts his
pencil at some focal point and draws the basic lines of his sketch so as
to radiate from that point, so should the cinematographer's lighting
radiate from this natural focal highlight-point in his scene. There
may be, and almost always are, secondary principal highlights, but
they should be distributed with pleasing relationship to this main cen-
ter of interest — and light.

Establishing motion picture lighting in this manner, and from this
viewpoint permits, even compels, the use of more natural lighting
effects. For instance, suppose that I am seated in a room at a desk.
A desk-light creates a strong focal highlight where I sit. Farther
down the room is an open window, through which the light from the
outside establishes a secondary highlight-area. If I rise from the

166 G. GAUDIO [J. s. M. P.

desk and walk to the window, I would pass through the shaded arc
and enter the area of the secondary highlight.

Ordinary set-lighting technic would do one of two things : It woulc
either create the two highlight-areas and leave a dark, almost opaque
shadow between them, or it would illuminate the whole room brightly,
making little or no distinction between the highlight-areas by the
desk «and the window and the surrounding and naturally shaded
areas. In one case, as I arose from the desk I should disappear into
the shadow and then emerge from it into the other highlight by the
window. In the other, I should be equally visible and probably
equally well lighted all the way from one position to the other.

I have been trying to light my scenes during the past year so that
the result would be more closely akin to what the eye sees in life.
Seated at the desk, I would be in the principal highlight-area, fully
illuminated and modelled. So, too, would I be illuminated when stand-
ing at the window. The lighting would be so arranged that the illu-
mination would fall off gradually, as it would in actuality, as I moved
away from the desk-lamp; and then slowly increase again as I ap-
proached the light from the window. The audience would be aware
that I had moved out of the sphere of one light-source into that of an-
other. I would not be unnaturally illuminated as I crossed the room ;
neither would I vanish into pitch-black shadow. If the lighting that
produced the proper effect when I was not standing in one of the prin-
cipal light centers should not produce the required modelling of my
form when I was standing in one or the other position, additional
spotlighting units could be brought up with dimmers as I approached,
and dimmed again as I left. Properly done, this change in lighting
would not be evident as a change upon the screen.

The same technic can be used just as well for moving-camera shots,
for following an actor in his movements about the room. In fact, it
enhances the effectiveness of such shots and strengthens the impres-
sion of moving about with the player. One does not, if he is walking
through an average room with another person, expect to see the per-
son always perfectly illuminated as he moves from the region of one
light or window to that of another. Why, then, should it be so s
in a picture?

In both of my most recent productions, Anthony Adverse and
Zola, most of the moving-camera shots have been lighted so as to
simulate natural effects, letting the players move through the less
brilliantly lighted areas, and concentrating the highlights and the

Aug., 1937 J LIGHTING OF MOTION PICTURES 167

modelling effects in what would in actuality be the logical highlight-
areas. I try, of course, to make those points coincide with the dra-
matically important parts of the scene, and especially with the spots
where the characters stand still for any length of time. The result
upon the screen is more convincingly natural, and both audiences and
critics have accepted the results very favorably.

The scene in White Angel in which Kay Francis, as Florence
Nightingale, walks, candle in hand, through the long hospital wards
at night ministering to the wounded soldiers, was lighted in such a
manner, the lighting that played upon her at each stopping point
being controlled by dimmers.

From this discussion it will be seen that this form of lighting must
of necessity be very closely interlocked with the composition of the
scene, just as it should be, for composition is really much more than
the mere geometrical arrangement of lines, masses, and objects.
Composition should properly take into consideration lighting; and
lighting, composition. The best composition can be ruined by in-
correct lighting. Technically excellent lighting can be bad if it is
not properly coordinated with the composition. The two are, in
fact, so closely related that, as one of my colleagues once remarked,
"If you light the scene properly, the composition is half made; if you
begin by composing the scene properly, and light accordingly, the
lighting is half made before you touch a single lamp."

The technic described here requires neither more angles of illu-
mination nor more lighting units than the conventional general-
lighting-plus-spotlighting technic. Far from requiring a higher level
of illumination, it permits, as a rule, the use of lower levels. It en-
ables the cameraman to take more complete advantage of today's
films, lenses, and lamps. It greatly simplifies both the lighting and
the photographing of modern moving-camera scenes.

It must be admitted that this kind of precision lighting is not, and
can not be, so routine as the more conventional methods of lighting.
It can not be hurried through carelessly, or by roughly applying a
set formula. It definitely requires that the director of photography
be alert at all times. But the results upon the screen are immensely
more satisfying, not alone in that they can be more artistic, but that
they become more natural; and naturalness is the elusive element
that all of us most earnestly strive to reproduce upon the screen.

168 G. GAUDIO

DISCUSSION

MR. MORGAN: Are polarized screens being used for dimming?

MR. GAUDIO: They are applied more to exteriors, where there is considerable
reflection of light ; but not to interiors.

MR. MORGAN: What method do you use for dimming the lights?

MR. GUADIO: We use the set of dimmers, as explained in the paper. We mark
the dimmer so that when the actor turns around the intensity is greater than
it was when his back was toward the camera. The dimmers turn with the same
speed as the actor and when his face is toward the camera it will be lighted in good
balance instead of being a black silhouette.

Referring to the example mentioned in the paper, the window was no farther
from the actor in either instance. If I had used a flare light on the face, the wall
beneath the window would have been flooded with light. The depth and the
apparent distance of the actor from the back wall would have been lacking. Six
or eight spots covering the area including the face would keep the wall at the same
intensity as when the actor had his back to the camera.

MR. MORGAN : What method of testing do you use?

MR. GAUDIO: Sometimes I use a photoelectric meter. The cameraman may
not need a meter for small sets, of which he has previously made other pictures;
but whenever I am in doubt, I make the tests in cooperation with the laboratory
or the camera department.

MR. HAWKINS: For television we have equipment that is comparable to the
old insensitive film. We require strong back lighting so that the characters will
stand out from the background. Do you recommend the old overhead high-
level illumination, or could we use your method of lighting?

MR. GAUDIO: I am quite ignorant of the technic of television, but speaking
photographically, if you need very strong light to bring out the actors pronounc-
edly I suggest that you use the high level. There is no objection to doing so. With
a strong spotlight you can get all the intensity you want, and build up the face,
and the background will remain unchanged. If the front is built up with flood-
lights, the background will also be in the floodlight. I eliminate the floodlights
from the floor because with them I can not control the depth as well as I can with
the spots.

MR. LUBCKE : Is your lighting different for different types of films?

MR. GAUDIO : No. You heard Fred Jackman's paper : On account of the screen
reflection, Mr. Jackman does not use floodlights. Spots do not interfere with
the background but provide the quality and the density, and the highlights and
the shadows.

Of course, sometimes, different quality is required: You would not want the
same lighting effects in a comedy as you would in a dramatic production. How-
ever, last year, when making The King and the Chorus Girl I did not change any of
the technic at all, except as to the brilliance. Light comedy requires more bril-
liance than does a picture like the Life of Louis Pasteur, but the routine technic
is exactly the same.

THE ADVANCED TECHNIC OF TECHNICOLOR LIGHTING*

C. W. HANDLEY**

Summary.— Within the past several months the technic of lighting Technicolor
motion pictures has changed from more or less flat, evenly illuminated sets of high-
light level to a method whereby the cinematographer now uses a much lower level of
general illumination and has greater freedom with the use of "modelling" lamps.

Recent developments in arc lamps for use in Technicolor lighting are discussed.
The changed technic of lighting, made possible by the new equipment and the labora-
tory advancements, is briefly explained. The uses of each type of illuminant, diffu-
sion screens, black screens, and other lighting-control devices are described. An
explanation is given of the part taken by the chief set electrician, or "gaffer" in
lighting motion picture sets.

A previous paper1 described the studio illuminating equipment used
for Technicolor productions in 1935. Since that time developments
in arc lamps and changes in the Technicolor process have occurred
that represent considerable advances in the technic of Technicolor
lighting.

The last report of the Studio Lighting Committee2 gives the aver-
age light-intensity used on black-and-white sets as 250 to 400 foot-
candles, and on Technicolor sets as 800 to 1000 foot-candles. Dur-
ing the past year Technicolor has been able to reduce the illumination
by more than 40 per cent, and in some cases to approximately the
same levels as now used for a great deal of black-and-white work.
These changes have been made possible by the use of more efficient
lighting equipment, changes in the Technicolor photographic technic,
and advances in the art of laboratory processing.

When the first Technicolor three-color picture was made the MR-29
twin-arc broadside and the MR-27 Scoop3 were the only modern arc
lamps available. These lamps were developed for general illumina-
tion in Technicolor photography, and were placed around and above
the set in such a manner as to establish a uniform overall illumination.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 4, 1937.
** National Carbon Co., Cleveland, Ohio.

169

170

C. W. HANDLEY

[J. S. M. P. E.

The spotlamps and Sun arcs used for creating areas of higher inten-
sity, such as through doors and windows, back-lighting, streak-
lighting, etc., were lamps that had been used for many years on black-
and-white productions. Although they delivered more light on the
set than the scoop or broadside, they did not give as even a field, nor
were they as quiet, or as good in color quality. Therefore, the broad-
side and scoop were used wherever possible. As a result of these

conditions a great many more lamps
were used on the sets than would have
been necessary if modern high-intensity
equipment had been available.

NEW ARC LAMPS

One of the new lamps recently de-
veloped to meet Technicolor's needs4 is
shown in Fig. 1. Figs. 2, 3, and 4 show
the light distributions of the new units
in comparison with the distribution of
the old type 36-inch Sun arc shown in
Fig. 5. The decided advantages of the
new lamps from the standpoint of uni-
formity of field, intensity, and beam
control are quite apparent.

The MR Type 90 lamp is now used in
place of the older 80-ampere rotary
spot.1 Although the two units are of
approximately the same size and weight,
the Type 90 at a beam-spread of 40
degrees delivers more than three times
the light of the 80-ampere rotary, and
at a beam-spread of 16 degrees twelve
times.

Concentric plano-convex lenses made of circular prisms are used in
the new lamps, with the arc crater facing the lenses so as to eliminate
all shadows of the lamp parts. With the old-style 36-inch Sun arc
(Fig. 5), the drop in illumination at the center of the field is caused by
the shadow of the positive head in the beam reflected by the mirror.
The 36-inch Sun arc is still used where a deep penetration of light is
desired on particularly long throws, or where very sharp shadows are
necessary.

FIG. 1. One of the new
lamps developed for Tech-
nicolor productions.

Aug., 1937] TECHNIC OF TECHNICOLOR LIGHTING

171

FIG. 2.

FIG. 3.

FIG. 4.

FIG. 5.

FIGS. 2, 3, and 4. Light distribution curves of new units.
FIG. 5. Light distribution curves of old type 36-inch Sun arc.

172

C. W. HANDLEY

(J. S. M. P.

LAMP FILTERS

The spectral distribution of the radiant energy from the mo tic
picture studio carbons1 used in the broadsides and scoops is such that
no filters are used unless certain special color effects are desired.
With the high-intensity carbons used in the spotlamps and Sun arcs,
however, the radiant energy in the blue and near-ultraviolet portions
of the spectrum is too great for proper color balance. Therefore, a
straw-colored gelatin filter is used in front of each of these units.

Here again Technicolor has effected a saving in light, since, by the
use of non-fugitive dyes, they have succeeded in producing a gelatin
that does not fade and whose transmission can therefore be relied

10

H.I*

U-ra. H.I. Hegatir*
150 jnp«r*s, 81 Tolta 4-«.

13.6-ou H.I.

7/16 •.«. Orotip

185 Amp«r«a, 63 Volts d-».

. High-Low Posltlr*

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I I I

4000

5000
Angstrom Unit*

6000

7000

FIG. 6. Spectral energy distribution curves of high-intensity carbons
through YI filter (positive crater radiation only).

upon. It was necessary to judge by eye the transmission of the first
unstable gelatin filters each time they were placed in use, and it was
common practice for that reason to use double thicknesses on certain
lamps as a matter of protection. Fig. 6 shows the spectral energy
distributions 9f the high-intensity arcs with the special straw YI
filter, as employed in the lamps.

ADVANCED LIGHTING TECHNIC

Improvements in the laboratory processing of the film, details of
which are outside the scope of this paper, have made it possible to
change the illumination technic from that of more or less flat lighting
with a uniform overall light intensity, to an advanced color technic
with widely varying levels. The new technic allows the cinematog-

Aug., 1937]

TECHNIC OF TECHNICOLOR LIGHTING

173

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C. W. HANDLEY

[J. S. M. P.

rapher to use ari abundance of modelling light, reducing the int
in the shadow areas, and thereby effecting a further saving in light.
The unrestricted use of modelling lamps of suitable intensities has
given the color cinematographer the same tools that are used in black-
and-white work, and the cinematographer 's artistry is not hampered
by technical limitations.

In preparation for lighting a motion picture set, a conference is
usually held between the cinematographer and the chief set electri-

FIG. 7. A scene from Vogues of 1938, showing the lighting equipment used
at the present time. (Courtesy Walter Wanger Productions.)

cian. In deciding upon the general level of illumination the cinema-
tographer considers the speed of the photographic equipment, the
requirements of the producer and director, the mood of the story, the
color of the set, and many other remote factors, all of which makes of
him an artist rather than a technician.

The chief set electrician or "gaffer" is the lighting technician on
the set. He directs the placing and control of equipment up to the
point where artistry enters. He knows from experience what each
lamp will deliver, where it is best used, and the number of units re-
quired for a given effect. If he has worked with the cinematographer

Aug., 1937] TECHNIC OF TECHNICOLOR LIGHTING 175

previously he is usually able to establish the positions of all general
equipment.

As a result of his conference with the cinematographer the set
electrician orders lamps to be placed upon the floor, behind doors and
windows, and on parallels constructed around the walls of the set.
When he has finished "roughing in" the lighting equipment the set
is illuminated in such a manner that it could be photographed without
change and a technically satisfactory negative would result.

Now the cinematographer takes charge. He orders frosted gela-

FIG. 8. A scene from Kid Millions, an early Technicolor three-color se-
quence, showing the lighting equipment used at that time. (Courtesy Sam
Goldwyn Productions.)

tin or silk screens placed over certain lamps to reduce the intensity and
to diffuse the light emitted from them. In other areas he raises the
light-intensity by adding more lamps or by reducing the beam-spread
of the units already in place. Other lamps are moved to stations
where they will better establish the effect he desires. Black screens,
called "gobos," are set at various points to keep the light from reach-
ing places where it is not desired or where it may interfere with the
free movement of the actors. He establishes points of deepest
shadows and brightest highlights. Between these points he manipu-
lates the equipment until the set is "modelled" into an area of high-

176

C. W. HANDLEY

[J. S. M. p.

lights, middletones, and shadows that blend with the mood of tt
story.

Because the lighting of a motion picture set is often a compromise
between the cinematographer's desire for a given effect and the
limitations of the equipment and process, it is difficult to attempt to
state the number of lamps required for any given area. Table I
lists the types of equipment used by Technicolor; Table II details
the various units used in photographing the huge ballroom set of
Becky Sharp, Technicolor's first three-color feature picture. The
quantity of equipment used was based upon an estimate given by
Ray Rennahan, chief cinematographer for the picture. Table II

TABLE II

Comparison of Quantity of Lighting Equipment

Lamp Equipment Used on
Becky Sharp Ballroom Set

Quantity

36* Sun Arcs 19

24* Sun Arcs 47
100-amp. Rotaries 4

80-amp. Rotary Spots 87
35-amp. Spots 1

Broadsides Type M-R29 71

Scoops MR-27 78

MR Junior Spots 12
36* Sun Spots 9

24* Sun Spots 5

18* Sun Spots 5

Rifles 5

Domes 1

Strips 40

Corresponding Equipment That Would

Be Used under Present
Lighting and Photographic Conditions

Quantity Quantity New Type

Total Lamps

384

4
None
None
None
1
35
40
12
5
None
None
None
None
None

30 MR-150's
40 MR- 90's

Total Lamps

167
12,895 Amps.

Generator Load at 115 Volts 20,000 Amps.

also shows Mr. Rennahan's estimate of the lamp equipment
would be required for the same set under present conditions of light-
ing. The reduction from the earlier requirements is apparent.
Figs. 7 and 8 also illustrate the difference.

According to William V. Skall, Technicolor cinematographer, a
further saving of light has been made possible because the new lamps
afford better control. Figs. 2, 3, and 4 show that these new units emit

Aug., 1937] TECHNIC OF TECHNICOLOR LIGHTING 177

a very even field of illumination at various divergences. The slopes
of the curves occur where the light from one lamp overlaps that from
another, thereby making it possible to balance the light in any desired
area with a minimum use of silks, jellies, or gobos, to cut down or
block out undesired light.

William Howard Greene, Technicolor cinematographer, states that
at the present time there is very little difference between lighting a
Technicolor set or a black-and-white set. The cinematographer now
has the freedom of black-and-white with the additional advantages of
depth and beauty that natural color affords.

REFERENCES

1 HANDLEY, C. W.: "Lighting for Technicolor Motion Pictures," /. Soc.
Mot. Pict. Eng., XXV (Nov., 1935), No. 5, p. 423.

2 Report of Studio Lighting Committee: J. Soc. Mot. Pict. Eng., XXVIII
(Jan., 1937), No. 1, p. 32.

3 MOLE, P.: "New Developments in Carbon Arc Lighting," /. Soc. Mot.
Pict. En&., XXH (Jan., 1934), No. 2, p. 51.

4 RICHARDSON, E. C.: "Recent Developments in High-Intensity Arc Spot
lamps for Motion Picture Production," /. Soc. Mot. Pict. Eng., XXVIII (Feb.,
1937), No. 2, p. 206.

RECENT DEVELOPMENTS IN MOTION PICTURE SET

LIGHTING*

E. C. RICHARDSON**

Summary.— The basic principles of motion picture set lighting are outlined,
the technic of "key" lighting, employed by most cinematographers, is discussed.

Several new types of lamps that have found extensive use are described in detail.
Technical data regarding them are presented along with information regarding their
application in cinematography.

Any discussion of motion picture set lighting should be prefaced by
acknowledging the fact that modern lighting is in practice susceptible
of almost infinite variation. One could go into any studio, and, con-
sidering the work of two equally prominent cinematographers, find
that although the two undoubtedly base their technic upon similar
principles, use the same tools, and obtain very similar results upon
the screen, their detailed methods as measured by the quantity of
light used, the number of units, and the way in which the lighting is
balanced, would differ greatly.

It is therefore manifestly impossible to set up a fixed rule and say
that, for a set of given size, so many foot-candles from each direction,
making such and such a total, will be required. Such a formula could
be devised, perhaps; but it would deal simply with illumination — not
with lighting, as it is understood and practiced here.

In previous discussions of the evolution of motion picture lighting,
it has frequently been pointed out that the modern lighting technic
evolved, bit by bit, from the very early necessity for a sufficient in-
tensity of illumination to permit an exposure. It was found, as soon
as artificial light-sources began to supplement the less controllable
natural illumination, that projecting beams of light upon sets and
actors from a variety of angles could give improved effects of depth
and roundness to the picture. The development of lighting from
that time has been closely interlocked with the development of light-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 20, 1937.

** Mole-Richardson, Inc., Hollywood, Calif.

178

DEVELOPMENTS IN SET LIGHTING 179

projectors affording more precise control of these beams. A similarly
important factor has been the introduction from time to time of more
highly sensitive emulsions, permitting a decrease in the overall illu-
mination level and making more precise control of the intensity and
divergence of light-beams desirable.

This is very well illustrated by comparing the so-called "general"
lighting of a few years ago with current practice. This phase of
lighting, as the name implies, deals with the maintenance of a defi-
nite overall level of illumination throughout the set. Until relatively
recently this was most generally achieved by means of the so-called
"general lighting units" — the broadside, the "rifle," the multiple-
unit "bank" and overhead "scoops" and "strips." The primary
function of these units was to establish a uniform overall flood of light
covering a vertical and horizontal spread of sixty or more degrees.
These units, especially the broads and rifles, mounted upon pedestals
on the stage floor, were arranged uniformly in rows on each side of
the camera. Sometimes such lamps would also be positioned upon
the lamp-rails at the tops of the sets. In the case of deep sets which
could not easily be penetrated by the floor units, in instances where
particularly high levels of illumination were desired, as in earlier
color processes and in black-and-white musical revue numbers, addi-
tional general lighting was commonly provided by scoop and strip
.units suspended above the set.

This general lighting provided foundations of even, diffused illu-
mination throughout the sets, even in the deepest shadows. The
necessary intermediate tones and highlights were built up from this
by means of more intense beams projected by the spotlighting units.

Within the past year, however, this rather characterless overall
lighting has been definitely on the wane. Today, we have reached
a point at which it can be said that this kind of lighting is definitely
on the way out. A number of factors have contributed to the change.
For one thing, we have put behind us the early-talkie technic of using
a multiplicity of cameras on every scene; and, through experience,
cinematographers have learned how to light moving-camera shots
more normally than was at first deemed necessary. Second, new
materials and still faster, emulsions have made flat foundational light-
ing more and more unnecessary, while the development of new and
more accurately controllable light-projecting units has made it
easier to light sets with precision.

There has, moreover, been noticed a new conception of the whole

180 E. C. RICHARDSON [j. s. M. p. E.

problem of set-lighting. Not so long ago — and especially in the five
or six years immediately following the introduction of sound, which
for a time seemed to set cinematography back immeasurably — a set
was to a surprising extent viewed more nearly as something to be
illuminated than as something to be lighted. It had, in other words,
merely to serve as an acceptable background for the characters, rather
than to take its part as an integral part of the composition.

During the past few years, the concept has changed. It is no longer
enough merely to light the set to give some illusion of depth, and to
keep it in accord with the visual mood of the action. It must now be
lighted decoratively, as an important part of the composition. More
than a few of the industry's outstanding cinematographers have stated
that they lavish quite as much care upon lighting the set itself as
upon lighting the star actors.

Several well recognized means take care of creating the illusions of
depth and roundness. Depth, for instance, is most frequently
achieved by contrasting the illumination of various planes of the
scene. A relatively dark foreground can be more or less silhouetted
against a more strongly illuminated middle plane, beyond which the
next plane may be either darker or lighter, and so on. Generally
speaking, the plane in which the object or action of greatest interest
lies will be the most strongly illuminated, since the more highly
keyed lighting concentrates the attention upon that plane.

The illusion of roundness is achieved by highlighting curved sur-
faces with little catch-lights which give to the single eye of the :
camera something of the effect they give to normal binocular vision.
Modelling flat and angular surfaces is accomplished by contrasting
halftones of light. Protrusions and indentations in wall areas, for j
example, are not illuminated flatly, but in such a manner that there
are unobtrusive but still definite shadows that render the objects in
pseudo-relief upon the screen. These effects are most generally at- ;
tained with projecting or spotlighting units, mounted overhead, and
usually "crossed" ; that is, an object on the left of the camera will be
modelled by a beam striking it angularly from a lamp on the right of
the camera, and vice versa. At times, too, a beam may be played ver-
tically down the wall of a set from a lamp mounted directly above
upon the lamp-rail. This, however, is being done less and less, be-
cause unless the beam is masked from the wall, the result appears
artificial. Much more frequently the beam will be projected down- :
ward from front or side. In this connection, it may be mentioned

Aug., 1937] DEVELOPMENTS IN SET LIGHTING 181

that although the majority of sets are still three-sided, the lamp-rails
overhead are in an increasing number of instances four-sided.

Over and above these familiar effects, set-lighting is more and more
frequently employing the artifice of casting decorative shadow-pat-
terns upon otherwise flat wall areas. Properly executed, this trick
enhances the composition, and adds variety to the otherwise monot-
onous flat effect of the prevalent light-walled sets.

The technic of "key lighting," while it can not wholly be said to
have come into use only during the past few years, has certainly
gained in importance lately. Fundamentally, it refers to the logical
practice of lighting sets directionally; that is, keying the lighting to
some logical angle of lighting, usually suggested by the design of the
set. That does not mean that all the lighting should come from the
one direction, but that the predominant highlights should appear to
come from the direction of some source established by the scene.
For example, imagine a set representing a modernistic penthouse.
Let us say that on the left of the camera are broad windows through
which can be seen an expanse of New York's skyline, only slightly oc-
culted by skyscrapers. In reality, we should expect most of the
illumination in such a room to come from the obvious source — the
windows. In a key-lighted set, the dominant lighting would appear
to come from the windows, although actually it would not. A strong
source-light, probably from some unit like an H. I. arc, would project
a clear-cut beam similar to sunlight through the windows. The
primary modelling lighting on both set and actors would come from
angles suggesting the windows as the source. Beneath this key
lighting would still be the vitally necessary secondary modelling
lighting, coming from other angles, giving to the scene depth and
roundness that would not result if all the light came from the key
direction.

The key lighting does not by any means have to be obvious. It is,
in fact, best if it fits unnoticeably into the general scheme of lighting.
But by arranging the lighting to coordinate with a definite key-light,
the cinematographer is able to create effects affording a superior il-
lusion of actuality. Noticed or not, the effects are more logical and
believable. Effect-lighting may be called an exaggerated develop-
ment of this technic. Generally it refers to extreme and unusual
lighting, often appearing to come solely from one source, as from a
fireplace, table lamp, or the like.

The lighting of close-ups is too intricate a subject to be dealt with

182 E. C. RICHARDSON [J. S. M. p. E.

in detail at this time. In the first place, it is an intensely individ-
ual matter, varying not only with the technic of the individual
cinematographer, but with the requirements of each player: One
player, Marlene Dietrich, for example, may appear to best advantage
under strong key lighting projecting downward upon her face; an-
other, such as Mae West, may require the softest of diffuse flat light-
ing ; a third, for example, Irene Dunne, may look best when her face is
softly illuminated by focusing a "baby" spotlight fitted with a ma-
genta filter, into her eyes, to enhance their natural sparkle.

Speaking broadly, much of this personal lighting which was done
only a few years ago by diffused broadsides or rifles, is now done by the
more controllable beams of spotlights. The new Junior Solarspot is
a prime favorite for this service, while the newer 500- watt baby Solar-
spots are coming into increasing favor. The even distribution of
their Fresnel-type lenses, together with the greater intensity in com-
parison with conventional condenser-spotlights, and the wider range
of usable beam divergences when compared with mirror-type lamps,
are winning these units an important place in personal lighting.

In making moving-camera shots, in which the camera follows the
actor about the set, close-up or medium, it has become very popular to
mount a suitable lamp directly upon the camera-blimp. The "Handi-
lamp" or "Lupe" has been very popular, and more recently the more
precise small Solarspots are being used extensively for such service.

Individual dimming devices are being used more and more, so that
any given lamp may be dimmed imperceptibly as a character walks
into or across its beam, and then restored to normal brightness
afterward.

Until the last few months, the foregoing applied chiefly to black-
and-white cinematography. Due to various limitations, natural-
color cinematography was felt to require flatter lighting. Within the
past six or eight months, however, color cinematography has made
immense strides toward parity with monochrome. Great improve-
ments have been made both in negative processing and in printing
methods, which have made it possible to attain better results with
more normally lighted color scenes. At the same time, newer and
more efficient arc spotlighting equipment has been made available in
the H. I. arc and Ultra H. I. arc.

It is well known that the best results in interior natural-color cine-
matography are attained by using light^sources that closely approxi-
mate the spectral distribution of natural daylight. This presupposes

Aug., 1937] DEVELOPMENTS IN SET LIGHTING 183

arc lighting, although earlier arcs, in addition to their unsteadiness,
often emitted an overly bluish light. The present high-intensity H. I.
arc spotlights, as used in Technicolor production, have corrected these
faults. Careful attention to the physical and mechanical aspects of
the burning of the carbon eliminated the flicker, and improvements
in the carbon itself helped to reduce the excess of blue and ultraviolet
radiation. Today, the H. I. arcs burn almost as steadily as incan-
descent lamps, and require only very light straw-colored gelatin
niters for correction to daylight standards. Optically their construc-
tion is similar to that of the Morinc-lensed Solarspots ; like them, they
afford a photographically satisfactory distribution of light within
the beam at all divergences from 8 to more than 45 degrees.

Accordingly they are used identically in the way in which Solarspots
are used in black-and-white cinematography. A somewhat higher
level of illumination is still required for color, but it has been consider-
ably reduced of late, and is coming every day into closer agreement,
unit for unit, with black-and-white practice. The arrangement of the
lighting units for color is identical to the arrangement in black-and-
white practice. The formerly dominant general lighting units-
side arcs on the floor and scoops overhead — have virtually vanished,
except from unusually large sets. Speaking conservatively, more
than 95 per cent of the lighting of a Technicolor production is now
effected by H. I. arc spotlighting equipment. The methods and
effects are virtually identical to those in the best monochrome pro-
ductions. In some respects, it may be said that color lighting
methods and equipment are in advance of those commonly used for
black-and-white, but for economic reasons, rather than technical.
For color, it was necessary to obtain new lighting equipment through-
out; for black-and-white, replacement necessarily has had to be
slower, because a vast supply of usable though obsolescent equip-
ment existed. As the advantages of the newer technic, which may
be called "precision lighting," become more and more apparent, it
will not be very long until we shall find the old-time concept of set
lighting as floodlighting extinct, and replaced by precision lighting of
sets as well as actors with the more precise tools of modern spot-
lighting.

POWER-LEVEL INDICATORS FOR SOUND RECORDING*

F. L. HOPPER**

Summary. — The principles and characteristics of various types of power-level
indicators used in sound recording are described, including the copper oxide, various
vacuum-tube devices including the peak-reading meter, and the recording types of
meters.

Continuous measurement of the level variations of speech or music
handled by sound recording systems is essential to satisfactory opera-
tion. These measurements assist in the satisfactory delivery of
program material from its point of origin to the ears of those interested
in its reception. The device employed is called a volume or power-
level indicator. The purpose of the indicator is two-fold: it must
permit controlling the system to which it is connected so that its
practical operating limits are not exceeded, and it must be capable of
indicating a range of power-level variation with respect to these
limits. The character of the distortions that result from overloading
is too well known to require discussion here. The control of level
in a sound recording system is perhaps more important than that
ordinarily required in communication systems due to the use of
electromechanical devices as modulating units. These in general
have sharply defined overload points, and the effect of exceeding
these limits is quite detrimental to sound quality.

The characteristics that a power-level indicator should possess
vary with the service for which the device is intended. It is the pur-
pose of this paper to discuss the various types of power-level indicators
employed in sound recording and their characteristics.

While various types of devices are used, there are certain funda-
mental requirements to be fulfilled if the device is to be completely
adequate. The requirements may be summarized as follows :

(a) The power-level indicator should be easily read, and capable of being inter-
preted so that various observers may obtain substantially similar results.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
20, 1937.

** Electrical Research Products, Inc., Hollywood", Calif.
184

POWER-LEVEL INDICATORS 185

(ft) By the use of the power-level indicator it should be possible to modulate
fully the recording device without overloading it.

(c) A long-scale range is preferable, since for low-level passages it is essential
to make adjustments such that the recorded sounds will be above the noise level.

(d) It is desirable that the device have the same response characteristic as the
recording system with which it is used.

Most power-level indicators consist primarily of a rectifier of some
type and an indicating meter. The rectifier may be of either the
copper-oxide or the vacuum-tube type. The more flexible devices
usually have an adjustable attenuator and one or more stages of ampli-
fication preceding the rectifier and meter, while the simpler types
consist of only the copper-oxide rectifier, an indicating meter, and a
fixed or variable series resistance.

The meter is usually a d-c. milliammeter, which is operated by the
current from the rectifier or vacuum tube. In addition, various
types of meters are employed having various operating speeds and
amounts of damping. Proponents of the high-speed types of meter
claim that the rapid variations in the speech or music waves may be
more easily followed, and that advantage may be taken of this to
modulate the recording device more fully without detectable over-
loading. Advocates of the slow-speed meters claim that the rapid
movements are confusing, and that the slower movement more nearly
represents the integrated effect that the ear perceives. It should also
be mentioned that the kind of circuit associated with the meter may
have a decided influence upon its operating speed.

Since most d-c. indicating meters have uniform current scales, the
scale becomes non-uniform when calibrated in decibels, since the deci-
bel is a logarithmic function. Meters having uniform decibel scales
may be designed by properly shaping the pole-pieces surrounding the
moving coil so that the flux density surrounding the conductors in the
moving coil varies with the position of the coil.1 Use has been made
also of the logarithmic relation between grid current and voltage in a
vacuum tube to produce a logarithmic indication with the usual type
of meter. A description of some of the various types of power-level
indicators follows:

Copper-Oxide Type.— A copper-oxide rectifier and a d-c. indicating
meter together constitute the simplest device widely used for measur-
ing volume variations. The circuit of such an indicator is shown in
Fig. 1, and includes a series resistance for adjusting the sensitivity.
The circuit under measurement is connected through the resistor to

186

F. L. HOPPER

[J. S. M. P. E.

the full-wave copper-oxide rectifier, which in turn supplies current to
the indicating meter. Such devices usually have relatively high
impedances and may be bridged across 500-ohm circuits without in-
troducing excessive loss. They
indicate the average value of
the wave to be measured, hence
the meter deflection is propor-
tional to the input voltage.
The response characteristic is
usually uniform over the audio-
frequency range.
FIG. 1. Copper-oxide indicator. A more flexible type of vol-

ume indicator is shown in

Fig. 2. Here the copper-oxide rectifier and indicating meter are
preceded by a single-stage vacuum-tube amplifier provided with a
gain control.

A variety of indicating meters having movements of different
speeds are available. The high-speed types have excellent damping
characteristics, so that there is very little overswinging of the meter
needle. Where minimum space and equipment are essentials, these
instruments have found wide fields of use.

Thermocouple Type. — One of the earlier types of instrument em-
ployed a thermocouple in conjunction with a d-c. indicating meter.
The readings were a function of the PR losses occurring in the heater
element, and the action was slow due to the thermal inertia of the ele-
ments employed. The indications were proportional to the power
in the input wave integrated over an appreciable time.

FIG. 2. Copper-oxide indicator with amplifier and gain
control.

Vacuum-Tube Types. — A vacuum-tube power-level indicator is
shown in Fig. 3. The plate current from a .grid-biased vacuum-tube
detector operates a d-c. meter in the plate circuit. Since this type

Aug., 1937]

POWER-LEVEL INDICATORS

187

was widely used in communication work -when motion picture sound
recording began, it was generally adopted and has been used in sound
recording essentially without modification until recently.

The integrating grid-blocking type was one of the early devices
employing a vacuum tube. In this instrument the floating grid of a
vacuum tube was biased by the charge accumulated in a condenser
coupled to the circuit being measured. After a given length of time
the plate current of the tube was measured, and the voltage existing
on the grid determined from a previous calibration. The condenser
was then discharged and the device again connected to the circuit
under measurement. Such a device gives an integrated reading of
the voltage variations occurring in the measuring circuit over the
period of time during which it was connected. Since it does not

FIG. 3. Simple vacuum-tube indicator.

give a continuously varying reading, it has no practical application
to sound recording.

Peak-Reading Power-Level Indicator. — Peak-reading power-level in-
dicators give indications that are a function of the peak value of the
input wave2'3-4'9 and are essentially independent of form-factor. They
are adaptable to sound recording because such systems usually have
a sharply defined overload point, due to the electromechanical devices
used as modulating units. The overload point is therefore effec
tively determined by the peak value of the applied wave, rather
than by either the rms. or average value. The circuit of such a
power level indicator is shown in Fig. 4, and its operation is as follows :

The voltage to be measured is applied to the input, passing through
a network having the response characteristic of the system whose
volume variations are being measured. If the system is uniform in

188

F. L. HOPPER

[J. S. M. P. E.

response, the equalizer may be omitted. A sensitivity control (s)
precedes a stage of amplification (A). The amplified voltage is then
applied to a full- wave rectifier (R), the rectified voltage in turn charg-
ing a capacity (C) shunted by a resistance (r). The grid of a triode

//\r

FIG. 4. Peak -reading power-level indicator.

(T) is biased by the rectified voltage and controls the flow of plate
current through the indicating meter (M).

The speed of operation of the device is determined by the value of
the capacity (C) and the impedance of the rectifier. The restoring
time is a function of the capacity and the resistance that shunts it.
By properly choosing the circuit elements, fast operation with rela-
tively slower restoration may be attained. Such a condition is de-

IMPULSE DURATION IN MILLISECONDS
40 80 120 160

200

1 PEAK INDICATOR

2 HIGH SPEED COPPER OXIDE INDICATOR

3 USUAL VACUUM TUBE VOL. INDICATOR

FIG. 5. Operating speeds of typical power -level indi-
cators. (1) peak indicator; (2) high-speed copper-
oxide; (5) usual vacuum-tube indicator.

sirable because it permits more accurately determining the point to
which the meter needle is deflected.

A long-scale meter having suitable damping characteristics may be
used with such a circuit. Since the current through the meter is

Aug., 1937] POWER-LEVEL INDICATORS 189

maximum when there is no input voltage, the simple expedient of
mounting the meter upside down, or of reversing the meter move-
ment, permits reading the indications from left to right, as with ordi-
nary meters. Since the greater the applied voltage, the lower will be the
current flowing through the meter, it is impossible for excessive inputs
to damage the meter, as with most other systems. The meter is placed
in the cathode circuit and hence is practically at ground potential.

The operating speeds of several typical power-level indicators are
shown in Fig. 5. Impulses of varying duration were applied to the
inputs of the indicators. For a steady sine-wave input the meters
gave readings that, for convenience, were chosen as reference points.
For impulses of the same amplitude but decreasing duration, the de-
flections of the meter become proportionately less, approaching zero
as the impulse time approaches zero. The curve shows the impulse
time in milliseconds plotted as abscissa, and the meter deflection in
db. below the reference point as ordinates. The peak meter more
nearly approaches the steady-state reading for short impulses than do
the other types illustrated. The measurements were made in the
following manner : A tone- wheel was used to interrupt a light-beam
which in turn modulated a photocell. The resulting photocell current
was amplified and used as the source of tone for operating the volume
indicators. A calibrated variable-speed shutter interposed in the
light-beam made it possible to apply impulses of varying duration to
the power-level indicators under test.

Tests with this type of indicator showed that if the power-level
indicator had a fast operating and fast restoring time, peaks were
consistently read 2 or 3 db. lower than if the restoring time were rela-
tively long compared with the operating time. The slower restoring
time permits more accurate observation of the point to which the
needle is deflected.

Recording Power-Level Indicators. — For certain kinds of studio work a
continuous graphical record of volume variations may be desirable.
To obtain such a record, a d-c. operated recording chart meter may
be connected to the output of nearly any of the previously described
vacuum-tube power-level indicators. If a logarithmic deflection of
the chart meter pen is required, it may be obtained by appropriately
designing the meter or modifying the circuits supplying the meter.

Such a recording indicator may be used for routine studio trans-
mission tests, affording printed records that are quickly made and
filed for future record or reference. For certain special services,

190 F. L. HOPPER

such as re-recording, it has been suggested that some such printed
records of volume variations might be of value in determining the re-
corded volume range and number of overloads occurring in the re-
recordings.

Many other automatic curve-drawing instruments have been de-
scribed in the literature.8'6'7'8 In general, they are more elabo-
rate, employing motor-driven attenuators (to which a pen is at-
tached) that balance the variable input voltage to the device against
the output of its amplifier system.

REFERENCES

1 BEST, F. H.: "Decibel Meters," Bell Lab. Record, XV (Jan., 1937), No. 5,
p. 167.

2 THILO, H. G., AND BIDLINGMAIER, M.: "Die Tonmesser, ein sparrnungs
spitzenmesser mit logarithmischer anzeige," ENT, XIII (1936), No. 5.

3 JOLLIFFE, C. B.: "The Use of the Electron-Tube Peak Voltmeter for the
Measurement of Modulation," Proc. I. R. E., XVII (April, 1929), No. 4, p. 660.

4 "Thermionic Peak Voltmeter for Use at Very High Frequencies," /. /. R. E.
(London), 77 (Sept., 1935), No. 465, p. 429.

5 BEST, F. H.: "A Recording Transmission-Measuring System for Telephone
Circuit Testing," Bell Syst. Tech. J., XII (Jan., 1933), No. 1, p. 22.

6 BALLANTINE, S. : "Logarithmic Recorder for Frequency Response Measure-
ments at Audio Frequencies," /. Acoust. Soc. Amer., V (July, 1933), No. 1, p. 10.

7 SLONCZEWSKI, T.: "Automatic Measurement of Transmission," Bell Lab.
Record, XV (Oct., 1936), No. 2, p. 56.

8 PEACHEY, F. A.: "Automatic Line Level Recording Apparatus," Wireless
Engineer (Sept., 1936), No. 9, p. 462.

9 READ, S., JR.: "A Neon Type Volume Indicator," /. Soc. Mot. Pict. Eng.,
XXVIH (June, 1937), No. 6, p. 633.

DISCUSSION

MR. TASKER: There was no discussion of the neon volume indicator.

MR. HOPPER: That is true, Mr. Tasker. The reason for not discussing it was
the lack of published information relating to the subject. A paper was presented
at the Fall Convention describing such a device, but it has not yet been pub-
lished. Devices of this general type are capable of measuring wide volume ranges,
but are usually somewhat complicated electrically, and are difficult to read in the
presence of light.

Incidentally, we have made listening tests using a copper-oxide volume in-
dicator of high speed and a peak volume indicator. The peak meter was ad-
justed to have a slower restoring than operating time. Using these two types
of devices and listening to various sorts of dialog and music, picked up through a
recording channel and reproduced over a loud speaker from the photoelectric cell
monitor, the peak meter indicated very close correlation between overload as
read on the meter and that heard in PEC monitor ; while for the high-speed cop-
per-oxide type such close correlation did not exist.

LIGHT-WEIGHT STAGE PICK-UP EQUIPMENT*
L. D. GRIGNON**

Summary. — In the past year and a half light-weight microphones and new
pick-up equipment have been made available. The apparatus described in the paper
consists of a fish-pole type of microphone boom with accessories, and a complete stage
pick-up unit. The boom is readily adaptable to a number of pick-up conditions
where light weight, small size, and ease of handling are necessary.

The stage pick-up unit is readily portable and of relatively small weight and size.
It includes the pick-up amplifier, booster amplifier, and power supply, with a small
amount of storage space. It completely replaces the large type of monitoring booth
previously employed. The weight of the unit being about 300 pounds, a great saving
in operating cost is effected and greater simplicity of operation achieved.

Within the past two years Electrical Research Products, Inc.,
have made available to the industry certain equipment that can be
so combined as to provide complete small-sized recording units with-
out sacrificing fidelity. The items that primarily made this possible
were a new head-set having far greater frequency range than previously
obtained, the 630-A transmitter, and the type Q recording equipment.
Simultaneously, Paramount decided to modernize its recording equip-
ment. After tests of the new head-set had been made it was agreed
that the large-size monitoring horn and booth then being used could
be dispensed with, and the equipment combined into some sort of
dolly or cart.

The type Q recording equipment decided upon consists essentially
of three items: the pick-up amplifier, the main amplifier, and the
power supply providing complete a-c. operation. The requirements
for the dolly or cart were as follows :

(1) The weight of the complete unit should be no greater than two men
could handle on a set, or move from storage to stage.

(2) The size should be such as to allow working between lights, near the
action, through doors, etc.

(3) A small amount of storage space should be provided for scripts, circuit
drawings, microphones, and head-sets.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.
** Paramount Pictures, Inc., Hollywood, Calif.

191

192

L. D. GRIGNON

[J. S. M. P. E.

FIG. 1. Front view (open).

(4) The unit should be comfortable to operate.

(5) Pneumatic tires should be used, to reduce shocking the equipment during
transportation.

(6) It should be durable and maintain its finish.

(7) It should have a good appearance.

FIG. 2. Rear view (open).

Aug., 1937]

STAGE PICK-UP EQUIPMENT

193

Requirement 6 practically demanded metallic construction or
sheathing, and to conform to requirement 1 the choice must of neces-
sity be aluminum or duralumin. Duralumin was chosen. Small
pneumatic tires and wheels, intended for toy automobiles, were se-
lected to fit requirement 5. Requirement 4 indicated that the desk
should be of normal desk height. For the finish we decided to sand-
blast the duralumin and then apply a coat of clear lacquer, thereby
completing requirement 6 and fulfilling 7.

Having made preliminary drawings, the first model
was built by applying sheet duralumin over a plywood
frame, but the construction was somewhat laborious,
was not sufficiently rigid, and did not give the appear-
ance of a finished job. It was found that to eliminate
the wood frame and use duralumin completely would
add only very few pounds to the weight. The first
model, however, proved that a practicable size had
been achieved without undue weight and that the
fundamental idea of the design was correct. From this
the final units were designed.

Fig. 1 shows the front view of the unit with the
lid open. The drawer for scripts, reports, and draw-
ings is seen on the left. The chassis is made of Shelby
tubing pinned and welded together and then chromium
plated, all of which lends a somewhat modern appear-
ance. The bars on the sides are used to hold spare
microphone cable ends and to provide handles. The
castors were specially made so as to harmonize with
the design and enhance the appearance. The body
contains no wood except in the equipment panel and
desk, the assembly being made by welding and riveting
the 17 ST 14-gauge duralumin. The wood on the desk-
top is provided primarily to eliminate the coldness of the metal and
for easy replacement when the top becomes scarred from usage. The
body is held in place by four straps passing over the tubular chassis
and fastening to the ends of the body. For the sandblasting it is de-
sirable to use a very fine sharp sand at low air-pressure, otherwise
warping of the metal panels will occur.

The storage compartment in the upper left was provided for hand-
sets, head-sets, and microphones. The panel on the right carries the
main a-c. supply switch and stage warning lights, and has some space

FIG. 3.
"Fishpole"
type of hand
microphone
boom.

194 L. D. GRIGNON [J. S. M. P. E.

to spare for future devices. The pick-up unit is a standard RA 1001
amplifier, and a trap-door is provided in the knee space for access
to the vacuum tubes of this amplifier.

Fig. 2 shows the rear opened. The receptacles for the microphone
connections can be seen through the door of the upper compartment,
in which a lamp has been provided for illumination. In the lower
right compartment is located the RA 1002-A main amplifier, and in
the left the RA 1005 power supply for both amplifiers. The plugging
panel for stage cable is at the center. Metering the RA 1002-A
amplifier and the power supply is accomplished through doors in the
ends.

The whole unit, designated in the studio as a "stage pick-up unit,"

has a weight of 355 pounds,

J^AL ^f^^ of which 185 pounds is

'•»v^«k -^r ^^ equipment alone. The unit

^f^ ^ measures 56 inches long, 38

g^E| high, and 25 wide.

•PvKl^^ • As now used, this com-

^Pr^^ii^. ^^^ plete unit replaces a stage

^^^B ^^^ monitoring booth weighing

Bk about 2000 pounds and

containing wet and dry

B batteries, mixing panel, two

iJP^^ amplifiers, and monitoring

e, , t .. t -„„ A and talk -back horns. The

FIG. 4. Shock-proof mounting for 630-A

transmitter. pick-up unit also replaces

booster amplifiers previ-
ously installed in the recording building. In other words, it con-
tains a complete sound recording channel except for the recorder and
associated equipment, and the motor system.

LIGHT-WEIGHT BOOM AND MICROPHONE ACCESSORIES

The 630-A transmitter was mentioned earlier as a contribution
to lighter stage equipment, which is obvious when considering its
small size and its weight of only 14 ounces compared to the obsolete
394 condenser transmitter and 47 or 53 amplifier having a weight of
about 18 pounds. On certain kinds of shots the stage men found that
by placing the microphone at the end of a pole better pick-up results
could be achieved than could be attained with the large microphone
booms, and with a great saving in set-up time. As a consequence,

Aug., 1937]

STAGE PICK-UP EQUIPMENT

195

having received many demands for bamboo poles for this purpose,
we built a number of duralumin poles that telescoped from 8 to 15
feet. Fig. 3 shows the pole, commonly termed a "fishpole." The
assembly at the end, for supporting the 630- A transmitter, is insulated
from the pole by Lord rubber mountings, as shown in Fig. 4, and the
cable is supported internally by sponge rubber rings to prevent its
banging or sliding about and causing noise as the pole is handled.
As it becomes quite an impossible job to hold this pole continuously

FIG. 5. Light roller standard for "fishpole" boom.

during a long scene, two bases were constructed so that the pole
could be used on the base or removed and held in the hands.

In Fig. 5 is shown a standard mounted upon a common 18-inch
lamp-stand and equipped with a roller at the top. The roller is made
of leather disks bound together by two duralumin disks. The stand-
ard is free to rotate on its axis. The unit is operated by one man who
grasps the rear end of the pole and moves it about, up or down, in
or out, as the action requires.

196

L. D. GRIGNON

Another base, still in the experimental stage, is shown in Fig. 6.
In-and-out motion is accomplished by moving the front upright sec-
tion of the parallelogram, and the up-and-down motion is achieved
by the handle at the rear. The weights provide a degree of counter-
balancing. The stand is again the commonly used 18-inch lamp-
stand. The in-and-out motion of the microphone is made approxi-
mately straight-line by making the rear upright of the parallelogram
somewhat shorter than the front. A total usable movement of 5

FIG. 6. Light-weight parallelogram boom.

feet is realized with this unit. Credit for the idea of using an un-
balanced parallelogram for this purpose is gratefully given to Uni-
versal Studios. Possible improvements of this preliminary design
are no doubt obvious.

Use of this equipment results in considerable saving, because less
labor is required to move equipment. The production company
can move from one set or location to another in less time, and opera-
tion is improved because the operators are less hampered by equip-
ment limitations.

SPECIAL ENGINEERING PROBLEMS IN A MOTION
PICTURE STUDIO*

W. T. STROHM**

Summary. — The Engineering Department at the Twentieth Century- Fox Film
Studios is responsible for the various technical operations of the studio, which can be
classified under the headings of Air-Conditioning, Plumbing, Foundry, Mechanical,
or Electrical activities. These responsibilities cover a considerable portion of the
technical activities of a studio, and a great deal of effort is required to take care of the
routine matters that arise each day. However, the interesting work of this department
lies in the special engineering problems that arise in the production of motion pictures.
The paper describes some of the various engineering problems that have been en-
countered in the production of motion pictures at this studio.

The Engineering Department at the Twentieth Century-Fox Film
Corporation Studios is responsible for the various technical operations
of the studio, which can be classified under the headings of air-condi-
tioning plumbing, foundry, mechanical, and electrical activities.
These responsibilities cover a considerable portion of the technical
activities of the studio, and a great deal of effort is required to supply
the studio with these services efficiently and smoothly.

One of the most important departments is the electrical, which is
divided into two groups. One is the operating group, which follows
each picture production closely and supplies all the requirements for
lighting the sets. The other is the maintenance and construction
group, which is responsible for all permanent equipment.

The head of the operating group attends the daily production meet-
ings and finds what the requirements of each company are for the fol-
lowing day. He sees that the sets to be used are rigged and supplied
with all the necessary equipment so that the shooting crew can walk
upon the set the next morning and go to work immediately. The
equipment must be removed from the sets promptly after the sequences
have been photographed and approved, and installed on working sets
with the greatest dispatch. One of his most important duties is to

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 20, 1937.

** Twentieth Century-Fox Film Corp., Hollywood, Calif.

197

198 W. T. STROHM [J. S. M. p. E.

schedule the equipment properly and keep it moving quickly from set
to set, as thousands of dollars in rentals can be easily incurred due to
allowing the lighting equipment to stand on sets that are dressed but
not working.

The chief electrician in charge of lighting on each set is called the
"gaffer." He and his assistant, the "best boy," must be able to meet
all requests of the cameramen on the set. They must have available
Sun arc lamps for shadow or sunlight effects, and diffusion disks of
every conceivable material to produce the degree of diffused light re-
quired on the face of the star. Each cameraman and each production
(color or black-and-white) requires a different assortment of lamps,
both incandescent and arc. Lamps with plain reflectors, special cor-
rugated or parabolic reflectors, spotlights with various lenses, lamps
with different degrees of adjustable diffusion or concentration, dim-
mers, lamps of various color characteristics, special effects to create
lightning, wind machines, portable generators, and a thousand and one
special items are in constant use. All this equipment must operate
silently so that it does not record, which is also a difficult problem at
times.

The maintenance and construction group install, operate, and main-
tain all permanent equipment. They operate and maintain the tele-
phone system which consists of a private branch-exchange with twelve
operators. They keep the lamp equipment in proper working condi-
tion, operate the power house, and maintain the lighting and power
system in the studio, and more than 700 motors having a total output
of 9000 hp. in this studio. The general lighting and heating load is
2400 hp., the total load being more that 11,000, which is equivalent to
that required by a city of 20,000 inhabitants.

The duties of the ventilating, plumbing, and air-conditioning groups
are obvious. All the stages, projection rooms, and executive offices
are completely air-conditioned. Due to the enormous volume of the
sound stages a large amount of equipment is required but the increased
efficiency of the production units has more than justified the cost.

The plumbing department maintains the water supply system, the
automatic fire sprinkler system, and a high-pressure gas system,
and also installs all the plumbing fixtures on the sets. One problem
that is troublesome at times is to supply the sets with artificial rain.
The rain must not fall in "chunks" in front of the camera, but must
consist of raindrops of normal size falling with required intensity.

The motion picture industry requires many devices for creating

Aug., 1937] SPECIAL ENGINEERING PROBLEMS 199

special effects for use by the various production units, most of which
are impossible to obtain commercially. In addition to these devices,
which must be built in the studio, there is always required a large
amount of mechanical work on the various sets, as well as having to
construct equipment such as camera booms, camera cranes, gas-
driven generators, special wind machines, lighting equipment of all
kinds, and special-effects equipment. For that reason the department
operates a design group, which prepares the plans; a foundry, which
supplies the castings; and a very completely equipped machine shop,
which fabricates all the various devices.

In addition to the normal routine work of the various groups,
special problems handled by the engineering department cover every
conceivable request that can be made by a dozen production units,
each busily engaged in making a motion picture. As an example, one
of the most interesting problems that required solution was the con-
struction of the ice-skating rink used in the recent Sonja Henie pic-
ture, One in a Million. This task was a little unusual, and it is believed
that this ice-skating rink was the first of its size and kind to be used on
a motion picture stage.

Heretofore, most ice-skating sequences in motion pictures have been
accomplished with artificial ice consisting of hypo, specially applied.
This artifice was at first suggested, but was instantly ruled out due to
the fact that the featured player is the woman champion figure
skater of the world, and artificial ice would not have been adequate to
serve the purposes called for in the picture.

The production executives asked the engineering department to
construct immediately a natural ice-skating surface to cover an area of
80 by 130 feet. The problem that the department had to overcome
was to construct and install the rink in fourteen days. It was believed
by the various contractors who estimated the job to be an impossible
task but the rink was completed within the required time, and Miss
Henie was skating on the rink and had approved it within that period.

A great number of problems presented themselves during the
course of the work. It would be impossible to list them all but a few
of the more important ones will be mentioned :

It was not sufficient to enclose the skating rink in a large stage and re-
duce the temperature of the entire stage below the f reezingpoint, because
the temperature on the set had to be kept high enough so that the
breath condensation of the players would not show up in intimate
close-up scenes. Due to the great difference in temperature between

200 W. T. STROHM [J. S. M. P. E.

that of the ice and that of the atmosphere on the set, a fog was created
that rose from the ice and obscured the figure skating of the star,
especially her feet. The situation was further complicated by the
tremendous amount of heat liberated by the large number of Incandes-
cent lamps necessary for photographing the set, which so increased the
temperature of the air as to make the freezing process a difficult task
and to cause more fog to rise from the ice.

Special provisions had to be made to keep the ice uniform and free
from irregularities at all times. Great precautions had to be taken to
keep the ice clear of small particles, which are bound to drop at times
from the catwalks and parallels on which the lighting equipment is
mounted above the set and on which a large number of men neces-
sarily work. If a particle no larger than a pin dropped upon the ice
it would soon adhere to the frozen surface, and at the speed with which
Miss Henie skates would present a danger to be considered and dealt
with promptly.

Another problem was that of providing heating arrangements for
the comfort of the actors on the set when they were not in front of the
cameras. This was solved by constructing specially designed dressing
rooms right on the stage itself.

As soon as the rink was constructed and operating properly, the
photographic department found that for a certain sequence there was
not sufficient contrast between the ice and the action to be photo-
graphed. "White ice" was requested for this sequence to improve
the photography. The request caused much head-scratching, but
was solved by painting the surface of the ice with white paint, after
which another quarter-inch of the clear ice was frozen over the paint,
resulting photographically in "white ice."

Another very interesting problem arose during the production of
Banjo on My Knee. The engineering department was called upon to
produce a river capable of handling house-boats such as were common
on the Mississippi River and to produce a storm on the river that
would wreck a house-boat of such size. A large moat was dug and
filled with water. Pumps capable of delivering 20,000 gallons of
water a minute converted the moat into a swiftly flowing and turbu-
lent river. For the storm that finally sent the house-boats to their
destruction, great wind machines were used, and six large spill buckets,
each containing 2500 gallons of water, were dumped into the stream
against the already swaying and pitching house-boats. Accompanied

Aug., 1937] SPECIAL ENGINEERING PROBLEMS 201

by flashes of lightning and peals of thunder the effect produced in the
finished picture was very satisfactory.

Problems of coordinating and timing the various special effects in a
picture often call for a great deal of ingenuity. An example of tuning
mechanical equipment occurred in the recent production On the
Avenue. A series of sets, each mounted on a movable train, had to
move across the stage in front of the camera exactly in time with the
recorded music. An electric truck was used to pull the train, and to
synchronize the speed of the truck with the music proved quite a prob-
lem. It was finally solved by ingeniously altering an electric welding
generator to supply the power to the truck, and an efficient and flex-
ible speed control was provided that could be exactly synchronized
with the music.

Each picture presents distinct and different problems that must be
solved before production is started. The foregoing examples give
some idea of the great diversity of the problems that are encountered
in a studio in addition to the regular routine work of the department.

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus are held, in which various manufacturers of equipment describe and demonstrate
their new products and developments. Some of this equipment is described in the
following pages; the remainder will be published in subsequent issues of the Journal.

A HIGH-PRECISION SOUND-FILM RECORDING MACHINE*

H. PFANNENSTIEHL**

A recording machine for use in present-day commercial production of sound-
film must not only be capable of propelling film at a constant velocity to produce
high-quality records but must also be designed for simple, rapid, and flexible
operation.

The Western Electric recording machine described in this paper was designed
to fulfill these requirements after an extensive investigation of approved studio
practices and of mechanical, electrical, and optical means best suited for sound-
film recording. It is ruggedly constructed of materials selected to give long life
with a minimum of maintenance, and all operating mechanisms are enclosed in a
compact housing of pleasing appearance.

Fig. 1 is a front view of the recorder with doors closed and film magazine in
place. Fig. 2 is a closed rear view, showing the housing on top, which contains a
film take-up and drag mechanism, and, at the bottom, four connectors into which
may be inserted plugs attached to cabling for all outside circuit connections.
The handwheel shown at the left end may be used for turning the film-driving
mechanism of the machine.

Film-Driving Mechanism. — The fundamental requirement of a film-recording
machine is to propel film past the recording light-beam at a constant speed. In
this recorder constancy of film speed is attained by a positive sprocket drive sys-
tem similar in principle to that employed in the Western Electric recording ma-
chine, which has been in use in studios since 1927, but incorporating a number of
improvements to assure even more constant and reliable film speed and, conse-
quently, sound records with greater freedom from flutter effects.

The film drive system may be seen in Fig. 3, which is a view of the film com-
partment of the recorder. The film is propelled through the machine by means
of two sprockets driven by a constant-speed motor and a worm reduction-gear

* Posthumous; presented at the Spring, 1937, Meeting at Hollywood, Calif.;
received May 24, 1937.

** Bell Telephone Laboratories, New York, N. Y.

202

NEW MOTION PICTURE APPARATUS

203

204

NEW MOTION PICTURE APPARATUS [J. S. M. p. E.

FIG. 3. Film compartment.

FIG. 4. Rear view, opened.

Aug., 1937] NEW MOTION PICTURE APPARATUS 205

system. The smaller pull-down sprocket located in the upper left-hand corner
of the compartment is directly connected to the gear system. It pulls the film
from the magazine and also holds back the film, as it leaves the recorder, against
the pull of the film take-up mechanism, thus isolating that section of the film
upon which sound is being recorded from disturbances in the magazine mecha-
nism.

The larger of the two sprockets located in the lower right-hand corner of the
film compartment is the sound sprocket, which propels the film past the recording
light-beam at the required constant speed. This sound sprocket has been de-
signed to be used with film having a shrinkage of as much as 0.1 per cent (which
is greater than found in film used for present-day sound recording) without intro-
ducing sprocket-tooth modulation in the sound-track sufficient to be noticeable
in high-quality records of either music or speech. The sprocket is driven by the
worm gearing through a mechanical filter which prevents slight irregularities pres-
ent in even the most accurately made gears from affecting the constancy of speed
of the sprocket. This mechanical filter, shown in Fig. 4, consists of an accurately
balanced flywheel rigidly mounted upon the sound sprocket shaft, and a viscous
damped resilient coupling connecting the flywheel to its drive gear. The damping
element consists of two sylphon bellows connected through a restricted orifice
and completely filled with a viscous fluid. Any variation in speed of the gear
system lengthens one of the bellows and shortens the other, thus forcing the vis-
cous fluid through the orifice and producing a damping action that effectively
prevents the flywheel from oscillating. The viscosity of the damping fluid does
not change sufficiently over the temperature range of +20° to 4-130° F. to
affect appreciably the damping action of the mechanical filter.

By properly proportioning the mass of the flywheel, elasticity of coupling
springs, size of orifice, and viscosity of damping fluid, the mechanical filter effec-
tively restricts variations in the speed of the sound sprocket to an imperceptible
amount, especially in the low-frequency range, where speed variations would
produce a "wow-wow" effect in sound records. It also rapidly stabilizes the speed
of the sound sprocket after the recorder is started, so that the recording of sound
may begin in less than two seconds after the motor has come up to its full speed.

The drive gear system is enclosed in a housing containing a reservoir of oil, oil
from which is circulated by means of a pump through tubing to the mesh of the
worm and worm gears and to the sound sprocket gear bearings, which are thereby
kept constantly flooded with oil while the machine is in operation. Effective
means have been employed to prevent leakage of oil from the housing, especially
into the film compartment. The level of oil in the reservoir may be checked
conveniently on a gauge-glass located in the film compartment.

Referring again to Fig. 3, it will be seen that threading the film through the
recorder is simple and rapid. After leaving the storage compartment of the maga-
zine, the film passes through a guide which holds it in focus for a slating device
(to be described later), over a roller to the pull-down sprocket, and thence over a
series of three rollers to the sound sprocket. The middle one of the three rollers is
mounted in a pivoted frame which is weighted to produce a definite and constant
tension in the section of the film passing between the two sprockets. This film-
tensionujg roller assists in keeping the film speed constant at the sound recording
point by maintaining a constant film load on the filtered sound sprocket. The

206 NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

roller of this series nearest the sound sprocket is equipped with spring-retained
flanges to guide the film past the recording light-beam so that the sound-track
is located within 0.001 inch of its correct position upon the film.

After leaving the sound sprocket, the film passes as a loose loop over guide roll-
ers and through a punch (to be described later), and thence over a guide roller to
the pull-down sprocket, which maintains the loop against the pull of the film
take-up mechanism. In going from this sprocket into the magazine, the film
passes a switch mechanism which is tripped when a loop forms in this section due
to any failure of the film to take up in the magazine. The tripping of this switch,
due to the piling up of film, closes a contact that lights a signal lamp on the in-
strument panel and also operates a relay to stop the motor. By this means the
is film is stopped before it can pile up in the machine and cause damage.

All film-guiding and controlling rollers are ruggedly mounted and rotate on
precision ball bearings having exceptionally low and uniform friction. They are
lubricated for ordinary life and sealed against leakage of lubricant and entrance
of dirt. The worm-gear and sprocket shafts of the film-driving mechanism are
also mounted upon the same type of ball bearings.

A brake is provided which may be operated from a lever on the instrument
panel to stop the recorder quickly after current to the motor has been cut off, and
thereby reduce film wastage. The brake may also be arranged to be operated by
an electromagnet for remote control.

The film take-up mechanism contained in the housing on top of the machine in
back of the magazine consists of a frictional slip clutch driven by a silent chain and
sprocket gearing from the main drive gears, and is arranged to be coupled to the
spool in the magazine upon which the film is wound. This slip clutch may be
adjusted while the machine is in operation. An adjustable slip friction drag
mechanism also is included in this housing which couples with the pay-off spool
in the magazine to prevent the film from unwinding too rapidly and to keep it
slightly taut as it enters the recorder. Either the Mitchell or the Bell & Howell
film magazine may be used with this recorder.

A film footage counter mounted on the right-hand door is so arranged that
when the door is closed it is coupled through gearing to the pull-down sprocket
shaft.

Fig. 5 is a front view with the doors opened exposing the film sprockets and
guide rollers, film punch mechanism, and shutter, in the film compartment at the
right; and in the compartment at the left, the recording optical system, light-
valve, monitoring system, slater, and drive motor. All manual controls for oper-
ating the recorder are accessibly arranged on an inclined instrument panel located
at the bottom of the housing.

Modulator and Monitoring System. — Light-valves and their associated optical
systems to modulate the recording light in either the standard or push-pull
method of recording may be interchangeably mounted upon an optical bench
located in the left-hand compartment of the recorder. This optical bench is
equipped with adjusting screws to locate the recording lamp and to focus the
recording light-beam upon the film.

Associated with the modulator is an optical system, photoelectric cell, and
amplifier which provide for high-quality photoelectric cell monitoring of either
standard or push-pull recording. In the optical system a thin glass plate, located

Aug., 1937] NEW MOTION PICTURE APPARATUS 207

in the recording light-beam, between the light-valve and the recording objective
lens, diverts about 10 per cent of the total useful recording light-beam projected
into the photoelectric cell, by means of lenses and a prism. The output of the
amplifier associated with the photoelectric cell is wired to a jack on the instru-
ment panel for connection to a monitoring head-set receiver.

The light-diverting glass in the monitoring optical system is readily removable
for cleaning. It may be replaced by a silvered mirror, so that all the recording
light-beam may be reflected into the photoelectric cell for testing purposes. A
jack located in the top of the amplifier and connected into the photoelectric cell
circuit provides means for connecting a microammeter inte the circuit for the
purpose of setting lamp current and the noise-reduction biasing current, checking

FIG. 5. Front view.

light-valve overload, or, in the case of previous lamp calibration, for checking
the light- valve spacing.

Accessories. — Several accessory devices that may be mounted as component
parts of the recorder are provided to facilitate such practices as marking the
"take" number of the record, punching an identification notch or hole into the
film and rapidly cutting in or out the recording light-beam. An automatic
switch for controlling the various operations in their proper sequence is also
provided.

The slater shown in the upper part of Fig. 5 is used to mark photographically
the "take" number of the film. It contains two counters: one located so that its
figures are visible through an opening in the left-hand door, when closed, and the
other located with its figures in the plane of the sound-track center-line. Upon
operating a push-button on the instrument panel, two lamps illuminate the

208 NEW MOTION PICTURE APPARATUS

figures on the dials of the latter counter, which are projected upon the sound-
track ar.ea of the film with a reduction of approximately 4 to 1. A lever on the
door steps the dials of both counters, which are geared together to operate in
synchronism so that the number appearing upon the door counter is the number
photographed upon the film. Additional identification marks may be photo-
graphed upon the film by inserting cards in slides adjacent to the illuminated
counter dials.

An electromagnetically operated punch unit located in the lower right-hand
corner of the film compartment shown in Fig. 5 may be used to punch a notch in
the edge or a hole in -the center of the film, as desired. A button on the control
panel is provided for operating the punch.

The projection of the modulated light-beam from the light-valve to the film is
controlled by means of an electromagnetically operated shutter located on the
wall between the film and optical compartments, as shown in Fig. 5. A switch
on the instrument panel is provided to operate the shutter, which opens or closes
in Vaoo second or less. At this speed a definite and sharp line is produced upon
the sound-track at the cut-off point, which may be used as a synchronizing mark.
The recording objective lens mounted on the shutter frame is adjustable by means
of a screw to locate the modulated light-beam at the proper distance from the per-
forations in the film.

A switch mechanism contained in the upper housing of the recorder is operated
from the main drive system to control various operations of the machine auto-
matically in proper sequence. When the recorder starts, the switch automatically
changes the current to the recording lamp from its "hold" to its "on" value so
that it is lighted to full brilliancy before recording begins; it opens the shutter to
permit the recording light-beam to be projected upon the film after the slater
marks in the sound-track area have passed beyond the recording point, thereby
preventing fogging the marks by the recording light, and it disconnects the battery
from the slater and punch so that these devices can not be accidentally operated
and damage the film while the recorder is running. Upon stopping the recorder,
the switch automatically restores the recording lamp current to the "hold" value,
closes the shutter, and restores the battery to the slater and punch.

Provisions are made to connect remote-control devices for operating the slater,
punch, shutter, noise-reduction circuit, etc.

This sound recording machine has been developed by the Bell Telephone Labo-
ratories to meet not only the studios' basic requirements, but to facilitate their
specialized methods. Thus has been provided a recorder that contains not only
the mechanical elements necessary to film propulsion and sound quality of the
highest precision, but also those conveniences demanded by the production
methods of the studios and their operating personnel.

A LABORATORY FLUTTER-MEASURING INSTRUMENT*
R. R. SCOVILLE**

Mechanical irregularities producing speed variations in recording and repro-
ducing machinery constitute a source of distortion of sound quality difficult to
diagnose and eliminate in the usual manner. Electrical measurements of such
distortion, and especially analysis of the variation rates present, have been found
to be an invaluable guide in attacking flutter problems. Such measurements have
been employed in various fields of recording and reproducing and certain instru-
ments used therein have been described in the literature.1- 2> 3

The instrument to be described here was developed primarily for measurements
in the laboratory of either frequency modulation (flutter) or amplitude modulation,
and no efforts have been spared to make it as complete and thorough in its func-
tions as could be desired. While the principle of operation is basically similar to
that of a portable flutter-measuring instrument described previously,2 it differs
in the provision of more extensive facilities for analyzing the variation rates
present.

General Description. — With the new instrument, frequency variations as low as
±0.01 of 1 per cent of a 3000-cycle signal may be detected and the rates between
the limits of 0 and 200 per second may be determined. Amplitude modulation
may also be measured with a maximum sensitivity of ±0.3 of 1 per cent, and
with rate determination as before. The instrument is thus sufficiently sensitive
to indicate the minimum perceptibility thresholds for either of these two types
of modulation.

The equipment weighs approximately 400 pounds complete, and is mounted as
a unit upon rollers to facilitate movement to the machinery being tested. The
appearance of the assembly is shown in Fig. 1. It is energized from a 110- volt,
a-c. line. Six milliwatts of input signal having a frequency of approximately 3000
cps. are required for measurement, but any other frequency between 2000 and
4000 may be measured, provided suitable correction factors are applied. No
other equipment than that shown is normally required, although, if desired, an
oscillograph may be connected for further refinements of measurement. The
instrument may be quickly and easily operated to furnish definite readings of
the frequency distribution of flutter which may be recorded upon a chart meter
if desired for permanent record.

Principle of Frequency Modulation Measurement. — The physical nature of fre-
quency modulation and the relationship to flutter in sound records have been
previously described in the literature,1 to which reference should be made for an
understanding of the fundamentals. The instrument herein described employs

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 25, 1937.

** Electrical Research Products, Inc., Hollywood, Calif.

209

210

NEW MOTION PICTURE APPARATUS

[j. M. P. E. S.

the "amplitude modulation" method of measuring frequency variation. This is
accomplished in the following manner, as shown in Fig. 2 :

A relatively high frequency of approximately 3000 cps. whose frequency modu-
lation is to be determined is filtered to remove noise, then impressed upon a modu-
lator, where it is heterodyned by a local oscillator of adjustable frequency. The
difference frequency is transmitted through a band-pass filter, which rejects the
unwanted modulation products so that a new wave is obtained having the same
number of cycles variation as did the original signal, but the mean frequency of

FIG. 1 . Laboratory flutter-measuring instrument.

which may be set to a definite value required for measurement. This new
wave is then impressed upon a frequency-discriminating network which con-
verts the frequency-modulated wave into one having amplitude modulation, the
conversion being such that the percentage of amplitude modulation obtained is
in linear proportion to the percentage of frequency modulation and independent
of the rate. This output is amplified, and then rectified and suitably filtered,
to produce a d-c. component whose amplitude is proportional to the mean in-
coming frequency, and an a-c. component which is the variation factor to be
measured. When no separation of the latter into its individual components is to
be made, the output is coupled by means of a transformer to a copper-oxide rec-
tifier and thence to a milliammeter (which may be a chart meter or an ordinary

Aug., 1937]

NEW MOTION PICTURE APPARATUS

211

meter as desired). The meter is calibrated • in terms of percentage frequency
modulation of the 3000-cycle signal, the following full-scale sensitivity ranges
being made available : ±0.1, ±0.2, ±0.5, and ±2.0 per cent, as read on a high-
speed movement type of volume indicator meter. Full-scale, 41/2-inch deflection
charts may be recorded with ±0.5 or ±2.0 per cent variations. The readings
given are in terms of variation on each side of 3000 cps. rather than in terms of
the total frequency change relative to the signal frequency, which is believed to
be in line with the definition of percentage modulation used in radio and other
fields.

To analyze the rate components in the flutter wave, a set of band-pass filters
with adjustable transmission ranges is interposed between the demodulator and
the above-mentioned meters. Each filter covers a rate band about one-half
octave wide, and twelve filter combinations are used to cover the range of 0 to
200 cps. Table I shows the bands available. Since, for the very low frequencies

TABLE I

Table of Measuring Bands and Method of Reading Charts

Measuring Band

1

2

3

4

5

6

7

8

9
10
11
12
13
14
15
16
17

Frequency Range

1

130
80
50

34 -
22 -
12 -
7 -
4.5-
2.5-
1 -
0 -
2.5-
4.5-
7 -

-200
-200
-130

- 80

- 50

- 34

- 22

- 12

7.0
4.5
2.5
1

4.5
7.0
12

Method of Reading Chart

Mean Deflections of Needle or Pen

12 - 22
22 - 34

Pen Swing — Peak to Peak

Rate Observation Only

involved, large values of inductance and capacity are required with a minimum of
resistance dissipation, a considerable amount of investigation was required to
produce a satisfactory coil and filter design. Rates from 2.5 to 200 per second are
analyzed by measuring the components transmitted through the band-bass filter.
To measure flutter rates of less than 2.5 cps., the flutter wave, itself, obtained
by the demodulating action of the instrument, is impressed upon the chart meter
so that it functions as an oscillograph. Low-rate variations are thus indicated by
the swing of the writing pen, which is proportional to the incoming frequency. The
amplitude of swing of the pen is constant for frequencies between 0 and 1 per
second, and by applying equalization, a range of uniform response between 1 and
2.5 cps. is provided. These two ranges are thus pen-swing bands as distinguished

212

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

from the other bands in which the mean deflection of the needle from zero serves
to indicate the components passed through the band-filters. All bands may be
converted to swing-bands by removing the rectifier and biasing out the chart pen
so that oscillograms may be made of rates up to about 25 per second, above which
the vibration of the pen is too greatly attenuated to produce useful information.
This method is indicated in the last five conditions shown in Table I, and furnishes
useful qualitative information as to the exact rates present. For oscillograms of
frequencies in the higher rate-bands wherein the chart pen will not respond, a
mechanical oscillograph may be externally connected to the instrument, and uni-
form indication of the exact frequencies present in each band may be obtained.
Satisfactory measurements can usually be obtained without so doing, however.
Fig. 3 shows a typical flutter analysis chart made of one of the older types of
theater reproducing machines. The percentage variation of signal frequency in
each band is indicated by the mean deflection of the curve above the base line, the

FIG. 2. Diagram of fluttering- measuring instrument.

height being calibrated directly in per cent variation as shown. Thus in the 2.5
to 4.5-cps. band a variation of approximately =±=0.04 per cent is indicated. This
rather small disturbance was due to a 3-per-second variation present in the film
used for test, and originated with the 32-tooth sprocket of the recording machine.
The next higher band, 4.5 to 7 cps., shows considerably greater amplitude, ap-
proximately ±0.14 per cent. This variation was a 6-per-second rate, due to
eccentricity of the 16-tooth filtered drive sprocket, as shown in Fig. 4. The suc-
ceeding bands indicate decreased amplitudes up to the 22- to 34-band, which rises
to a value of ±0.08 per cent. In this band the disturbing rate was 24 per second,
corresponding to the frame speed. Thereafter the readings fall off up to the 80-
to 130-cycle band, which rises to ±0.17 per cent. In this band the predominant
rate was 96 cps., corresponding to the number of sprocket holes engaged per
second. The total reading at the end indicating the summation of all the com-
ponents present shows ±0.3 per cent. In Fig. 3, the readings given show only
approximately what the disturbing rates are. The more exact rates as stated in
connection with Fig. 3 are determined from the chart oscillograms of Fig. 4. Here
the alternating flutter rates have been impressed directly upon the meter element
in such a manner that the element acts as an oscillograph. The paper speed cor-

Aug., 1937]

NEW MOTION PICTURE APPARATUS

213

responds to one second of time between each line of the chart, so that to determine
the rate the number of wave crests per interval of time is counted. In the" upper
left-hand chart of Fig. 4, variations between 0 and 1 cps. are transmitted most
effectively. Here a variation of about one per second is shown, which is due to
the natural period of the flywheel. In the succeeding chart variations between
1.0 and 2.5 cps. are accentuated. The next chart to the right is equalized to
emphasize 2.5 to 4.5 cps., which is followed by oscillograms of the higher rate bands
as marked on the charts. The 3-per-second and also the 6-per-second rates re-
ferred to previously are plainly visible. The 24-per-second rate may be counted
on the original chart, but probably will not be discernible in Fig. 4.

Since the dynamic response of the writing pen is decreased rapidly for rates
above 3 per second, there is shown a steady attenuation in amplitude as the rate

^

-1'

-h

il

~Y\

s

^

==^

^

rt

==i

4

^

' ~fr

,-^k

=i

m&

2.5-4.5O/

4.5-700.

7-I2O-

12-220.

22-340,

f=!

r=3

•

KH

H

^

1=4=
=h=

1 1 /,

1—TjL

CT'^i / =*=a

-H 1 /L^jL^^f

— / — / — / — / — / — / —

/ /- j=
1 1 "'? /j

34-50'X.

50-800.

80-130^ 130-2000. 2-2000.

TOTAL

FIG. 3. Percentage flutter-band analysis. Percentage variation is
proportional to amplitude above base line.

increases, but just sufficient amplitude is obtained to determine the actual rates
up to about 30 cps. Above this rate there is seldom a disturbing variation other
than that of 96 per second, due to sprocket-hole propulsion. Although the oscillo-
grams shown in Fig. 4 are used most frequently for the determination of rate, the
first two will also indicate percentage variation within their respective bands.
Thus in the upper left chart of Fig. 4 a variation having a peak-to-peak swing
within the range indicated by the arrows will be ±0.1 per cent for rates between 0
and 0.1 cps. The amplitude of the 1-per-second variation is shown to be approxi-
mately ±0.05 per cent. The second chart of Fig. 4 may be similarly used to de-
termine the amplitude of variations between 1.0 and 2.5 per second where such
components occur. Thus the amplitude of extremely low-rate variations may be
accurately measured, so that when supplemented by the percentage analysis, as
shown in Fig. 3, all rates between 0 and 200 per second are covered.

214

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

Chart Mechanism. — An automatic chart drive and switching system is used by
means of which measurements of the flutter spectrum are automatically made
throughout the range provided in the following manner: After adjusting the in-
put signal to its proper value and operating the heterodyne condenser to obtain
the correct measuring frequency, a switch is thrown causing a set of automatic
switches to connect in, successively, one filter after another, and for each condition
causing the chart motor to advance the paper for three seconds. Having gone
through the full number of measurement bands the action stops, leaving the
complete story written upon the chart, which the operator may examine at his
convenience. Should the automatic feature not be desired, any filter condition
may be manually switched in and a chart may be made or not as desired.

The chart meter used is a commercial recording milliammeter with 0 to 5-ma.
scale. It is driven by a 60-cycle synchronous motor, producing a chart speed of
3/4 inch per second. The dynamic response of the writing pen is practically

^

7

=

l=\

1=

=

=t

=±=

=

4 —

F^

OHO

I-2.5O

2.5-4.50-

4.5-70 O

7-I2O

12-220

22-

FIG. 4. Chart oscillograms for exact rate determination. Percent-
age not proportional to amplitude except in bands noted.

uniform from zero to 1 .0 per second, above which the response drops off steadily,
being about 50 per cent at 2 cps. and around 10 per cent of the static response at
5cps.

Principle of Amplitude Modulation Measurement. — The method of measuring
amplitude modulation in the original signal consists in substituting a resistance
pad for the frequency discriminating network (Fig. 2, A -A} and proceeding as for
flutter measurements, except that since the chart meter is insufficiently sensitive
for this measurement a special meter is used having its scale calibrated directly in
percentage of amplitude modulation. Full-scale indications of ±3.0, ±10.0,
and ±30 per cent are provided. The band-pass filters may also be employed in
these measurements. Although amplitude modulation is not frequently a source
of trouble in reproduction, it does occasionally occur in film recording and proc-
essing so that there is some value in being able to measure it.

No special provision has been made to eliminate the effect of amplitude modula-
tion in the original signal when measuring frequency modulation. Because of
the high conversion factor of the instrument in converting frequency modulation
to amplitude modulation, such amplitude effects as are Initially in the signal are
normally negligibly small compared to the converted amplitudes. As a pre-

Aug., 1937] NEW MOTION PICTURE APPARATUS 215

cautionary measure, when measuring film reproduction it is advisable to scan not
less than 0.020 inch away from the line of sprocket holes in order to avoid the
amplitude modulation caused by irregular development around the sprocket
holes.4

Auxiliary Equipment. — The accuracy of reading of the instrument is checked
by the use of a calibration set, which generates an artificial frequency-modulated
wave of known percentage and rate. This unit is mounted inside the doors of the
lower part of the case, and consists of an oscillator having rotor plates driven by
a variable-speed motor. As the plates rotate, the oscillator frequently is changed
to the extent desired, which may be adjusted by the controls of the instrument.
The rotor plates may be driven at any rate between Vz and 200 cps., and the
percentage may be set for any value between ±0.05 and ±2.0 per cent. If the
percentage indication of the flutter-measuring set is found to be in error, an adjust-
ment may be readily made to correct it. However, a high degree of stability in
the readings has been obtained so that adjustments need rarely be made.

A secondary standard for calibrating the flutter-measuring set is provided in
the form of a phonograph record having various percentages of frequency modula-
tion at a 100-cps. rate. This record may be played on a moderately good turn-
table, and calibrations are made only through the band-filter, which passes a 100-
cps. rate. The effect of turntable irregularities is eliminated, since such varia-
tions are generally of much lower rate than can be passed through the 100-cps.
band-filter.

Measurement of flutter introduced by recording machinery is usually made by
recording upon a film, which is subsequently reproduced and measured on a ma-
chine as nearly flutter-free as possible. One type of equipment used for this
purpose is a high-quality disk turntable carrying a drum around which a short
loop of film is wound and reproduced by optical scanning.2

The instrument described has been in daily use for nearly a year, measuring a
wide variety of recording and reproducing machinery for both film and disk.
Numerous cases have occurred wherein unsuspected sources of trouble have been
located that would probably have remained obscure without such analytical
measurements.

Although the instrument described may seem overly elaborate, the outstanding
results obtained have more than justified its use as a laboratory tool for the de-
velopment of new equipment and for the effective correction of faults with a
minimum loss of time.

REFERENCES

1 SHEA, T. E., MACNAIR, W. A., AND SUBRIZI, V: "Flutter in Sound Records,"
J. Soc. Mot. Pict. Eng., XXV (Nov., 1935), No. 5, p. 403.

2 SCOVILLE, R. R.: "A Portable Flutter-Measuring Instrument," /. Soc. Mot.
Pict. Eng., XXV (Nov., 1935), No. 5, p. 416.

3 KELLOGG, E. W., AND MORGAN, A. R.: "Measurement of Speed Fluctuations
in Sound Recording and Reproducing Equipment," /. Acous. Soc. Amer. (April,
1936).

4 FRAYNE, J. G., AND PAGLIARULO, V.: "The Influence of Sprocket Holes upon
the Development of Adjacent Sound-Track Area," J. Soc. Mot. Pict. Eng., XXVIII
(March, 1937) No., 3, p. 235.

MAGNETIC RECORDING-REPRODUCING MACHINE FOR OBJECTIVE

SPEECH STUDY*

S. J. BEGUN**

Experience has shown that in studying languages, elocution, singing, or other
subjects involving the use of the voice, it is most important that the student hear a
reproduction of his own voice. No one can hear himself as others hear him, due to
the fact that the speaker hears his voice not so much by sound transmission
through the air, as by bone conduction through his head. If the student could
hear his own voice as he hears the voices of others, he could readily perceive his
mistakes. Only by hearing a good reproduction of his voice is the student able to
study his voice objectively and improve and train it by self -correction.

In the past, only mechanical recording was available for voice training by self-
correction. However, to make a disk record and play it back requires manual
work and dexterity. In addition, each disk can be used for recording only once.
Since voice training by self-correction requires recording and listening frequently
to the recorded voice, a simple fool-proof recording system requiring no special
handling and enabling unlimited use of a single sound-carrier would be ideal.

Magnetic recording is the ideal medium for such objective voice study and
training. A single recording medium may be used over and over again for new
voice records. If desired, the record may be preserved and reproduced years
later. A small magnetic recording head records and reproduces the speech with-
out any observable change in the recording medium; the process of making a new
record obliterates the preceding record. The speaker can hear his voice as soon
as it is recorded, and can repeat the reproduction as many times as he desires.
A single push-button controls all the recording and reproducing operations. A
condensed description of the principles underlying magnetic recording has been
described previously in the JOURNAL.1

A new magnetic recording machine for speech and voice training has been de-
veloped (Fig. 1). The recording medium is formed by a helix of endless tape 150
feet long, guided by four rollers mounted at the four corners of a frame that fits
into a small cabinet or trunk. A spring-and-rubber mounted motor hi the bottom
of the frame drives one of the rollers through a belt and propels the tape at a con-
stant speed. Guide bars mounted hi front of the rollers maintain the proper
spacing of the loops of tape on the rollers. One loop of the propelled endless tape
is led between the two hinged halves of the small magnetic head mounted at the
top of the frame (Fig. 2) . A pair of recording pole-pieces and a pair of obliterating
pole-pieces are mounted side by side hi the magnetic head. A new record is made
by the conjoint operation of the obliterating pole-pieces which erase the previous
recording, and the recording pole-pieces, which make the new record. The re-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 28, 1937.

** New York, N. Y.
216

NEW MOTION PICTURE APPARATUS 217

cording pole-pieces are used for reproducing the sound. The amplifier and loud
speaker are mounted within the frame above the motor.

A panel on tLe front of the amplifier contains all the controls of the machine.
One line-switch connects the line to the amplifier, and another turns the motor on
and off. One jack provides a connection for a microphone plug or a phonograph
plug, and another provides a connection from a phonograph pick-up. A starting
button at the top of the panel is the sole operating control of the machine, and the
revolving indicator knob below the starting button indicates the progress of the
recording operation.

The machine is designed to make a 30-second record. When the two line-
switches are turned on, the machine reproduces, and will continuously repeat the
recording. Recording may be effected either by inserting the microphone or
phonograph cord plug into the proper jack. The recording is synchronous with
the rotation of the indicator knob, which makes one revolution in 30 seconds and
indicates upon the dial the progress of the recording. The magnetic tape, ap-
proximately 150 feet long, is sufficient for a recording of 30 seconds, which has been
found suitable for voice training, but longer or shorter recording periods may be

Loud Speaker

Recording Button
H^^MBm~

Motor Switch

Amplifier Switch

. — w!^m - Turntable Input

Microphone Input

Timing Dial

FIG. 1. Magnetic recorder-reproducer (front view).

provided. At the end of one revolution, the rotation of the knob is automatically
arrested and the machine again starts the continuous reproduction of the new
record.

In language study it is often important to compare a sentence recorded by a
teacher or from a phonograph record with the same sentence repeated by the stu-
dent. This may readily be done by turning the indicator knob during the recording
operation. During one part of the revolution of the indicator, the teacher records
a sentence, after which the student repeats the sentence during the remaining part
of the revolution of the indicator. If the student, after hearing the reproduced
sentence, wishes to improve his imitation of the teacher's voice, he waits until the
teacher's sentence is repeated by the machine, then presses the starting button,
and repeats the recording of the sentence while the indicator moves over a part of
the 30-second scale. As soon as the student has completed the sentence, he turns
the indicator back to the normal reproducing position. Immediately the machine
repeats the previously recorded sentence of the teacher, followed by the new re-
cording of the sentence by the pupil. The student is thus abl« to determine
whether he has improved his diction, intonation, or accent, and he may do so as
many times as he desires.

218 NEW MOTION PICTURE APPARATUS

With a high-quality microphone, a high-quality reproducer, and a suitably
corrected amplifier, the response curve can be made uniform from 100 and 8000
cps. The new machine is thus not only a mirror of the voice, but also an efficient
voice teacher. However, to keep the price low and make the machine generally

Recorder-Reproducer
Eraser Head

Magnetic Tape

Motor

FIG. 2. Magnetic recorder-reproducer (rear
view, opened).

available for language schools and private use, the machine may be equipped with
a carbon microphone and small loud speaker. It may also be provided with a
loud speaker that operates as a transmitter during the recording process.

REFERENCE

1 BEGUN, S. J. : "Recent Developments in Magnetic Sound Recording," /. Soc.
Mot. Pict. Eng., XXVIII (May, 1937), No. 5, p. 464.

DISCUSSION

MR. HOPPER : What is the speed of the tape as it passes the magnetizing unit,
what are the dimensions, and what is the volume range possible in this sort of
recording?

MR. BEGUN: The speed of the tape is approximately five feet a second. The
volume range is 35 decibels above the ground-noise level. The width of the tape
is three millimeters, and the thickness 0.008 millimeter.

FREDERICK EUGENE IVES

It is with regret that the Society records the death of Frederick E.
Ives, Honorary Member of the Society, and well known inventor and
research worker in the photographic, optical, and graphic arts fields

FREDERICK EUGENE IVES

for man)'- years. Mr. Ives died at his home in Philadelphia on May
28th. He was 81 years of age. A son, Dr. Herbert E. Ives, of the Bell
Telephone Laboratories, survives.

Mr. Ives was born February 17, 1856, in the little village of Litch-

219

220 FREDERICK EUGENE IVES [J. S. M. P. E.

field, Conn. When he was 11 years of age his father died, and he was
compelled to leave school and contribute to the support of his mother,
two younger brothers, and two sisters. For some time he was en-
gaged as a printer's devil in the office of the Litchfield "Inquirer."
Although his early schooling was meager, he soon acquired an interest
in optical and photographic subjects and began his long period of in-
vention when still in his teens.

While serving his apprenticeship in the printing office, he turned his
attention to photography and in 1875-78 was in charge of the photo-
graphic laboratory of Cornell University. During his four years at
the institution, he perfected a process of making photoengraved typo-
graphic printing plates from pen drawings. He also invented the
first halftone process that was developed commercially, making by an
ingenious and scientific procedure, plates identical in characteristics
to those used today, but stereotype instead of copper or zinc etchings.

In 1879 he became associated with the firm of Crosscup & West,
wood engravers of Philadelphia, for whom he set up an establishment
for producing photoengravings according to his process. During that
time, also, Mr. Ives developed the ether saturator— an intense light-
source which was first used in the projection lantern at the Franklin
Institute at Philadelphia, and for the invention of which he was
granted the medal of the Institute.

His inventions and practical developments in the field of photo-
engraving probably constitute Ives' greatest claim to fame, since the
enormous photoengraving industry of the present day derives directly
from his establishment in Philadelphia. His first process (1878) pro-
duced the graduation of line and dot through the use of a gelatin
relief and an inked stippled surface pressed against it. This process,
the first commercially successful halftone, he later (1885) superseded
by the optical method, using a cross-line screen, which is now uni-
versally employed.

Ives' work in color photography began about 1885, when he first
developed a practical method of color sensitizing, using cosine to-
gether with chlorophyll, to equalize the color-sensitivity of the plate.
Next came the development of trichromatic halftones by the additive
process, which resulted in the Ives Kromskop System. Various
medals and other honors were awarded to Ives for these inventions.
In addition to his work on the photochromoscope system and color
print processes, Ives is credited with the first original work on the
modern type of binocular microscope.

Aug., 1937] FREDERICK EUGENE IVES 221

In 1905 he developed the Tripak System of color photography for
amateur and professional photographers, and about the same time
produced his "universal colorimeter" and "tint photometer," intended
for industrial standardization and designation of colors.

One of Ives' inventions best known by those in the motion picture
field was his parallax stereogram for viewing photographic objects in
relief without using a stereoscope. In the field of color cinematog-
raphy, Ives has about twenty patents to his credit, resulting mainly
from his desire to produce colored pictures on regular single-coated
positive film. More than seventy patents were filed by him up to
1925, but in addition, many other inventions and ideas that were not
patented have been described by him in the literature, or have been
utilized by others.

From these early days, which have been sketched here very briefly,
the life of Frederick E. Ives was filled with scientific achievement in all
directions. The art owes much to Frederick E. Ives, and the Society
deeply mourns the loss of such a brilliant thinker, inventor, and pro-
fuse contributor to the arts of civilization.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D. C.,
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

Academy of Motion Picture Arts and Sciences, Technical Bulletin

(June 8, 1937)

Revised Standard Electrical Characteristic for Two-
Way Reproducing Systems in Theaters (p. 1).

(June 15, 1937)

Second Annual Report on Television from the Stand-
point of the Motion Picture Producing Industry

American Cinematographer

18 (June, 1937), No. 6

Technicolor Bringing New Charm to Screen (p. 234). W. STULL
Erickson Describes Triple Five-Studio Spot (p. 238). C. R. EKICKSON
Build Fastest Sky Camera to Shoot Eclipse (p. 252).

Educational Screen

16 (June, 1937), No. 6
A New Era in Visual Methods (p. 182). J. B. MACHARG

Electronics

10 (June, 1937), No. 6
I. R. E. Sees Projection Television (p. 7).
Television Terminology (p. 14).

Class A Push-Pull Calculations (p. 18) E. W. HOUGHTON

For Engineer-Photographers Only (Timing Control

Relay) (p. 22). D. G. FINK

An Amplifier without Phase Distortion (p. 26).

Journal of the Association of Cine Technicians

3 (June- July, 1937), No. 10

Evolution: A Peep into the Past (p. 41). C. FRIESE-GREENE

The Visatone System of Sound Recording (p. 47). H. J. ROUND

Journal of the Optical Society of America

27 (June, 1937), No. 6

Colorimetry: Preliminary Draft of a Report on No-
menclature and Definitions (p. 207). L. A. JONES

222

CURRENT LITERATURE 223

Kinematograph Weekly

243 (May 27, 1937), No. 1571

Printing with Non-Slip Apparatus — R.C.A. Model
(p. 53). R. H. CRICKS

La cinematographic frangaise

19 (May 28, 1937), No. 969
A New Ideal Portable Block Projector (Le nouveau

block projecteur ideal portatif) (p. ix). J. TURQUAN

Semi-Rotating Turret and Automatic Loading — Two
Innovations in the New Paillard Cine Camera (La
tourelle demi-ronde et le chargement automatique,
deux innovations de la nouvelle cine-camera) (p. xvi). H. PAILLARD

La technique cinematographique

9 (May, 1937), No. 77

Photographing the Interior of the Human Body
(Prises de vues a 1'interieur du corps humain)
(p. 929). H. GRAU

Optical Systems for Sound Films (L'eclairage du film

dans le lecteur de son) (p. 939). J. P. CORTET

Motion Picture Herald (Better Theaters Section)

127 (June 26, 1937), No. 13

Theater Acoustics Today: 2. Design and Construc-
tion II (p. 31). C. C. POTWIN

Photographische Industrie

35 (June 9, 1937), No. 23
Stereoscopic Projection with Polarizers (Raumlicher

Bildwurf mit Polarisatoren) (p. 639). BURKERT

Science et industries photographiques

Series 2, 8 (April, 1937), No. 4

Active Atomic Groups in Color Sensitizing with Ery-
throsine (Les groupements atomiques actifs dans la
sensibilisation chromatique par 1'erythrosine) (p. 97). G. SCHWARZ
Adherence of the Photographic Emulsion to a Cellulose
Acetate Support (Adherence de 1'emulsion photo-
graphique aux supports d'acetate de cellulose)
(p. 99). A. CHARRIOU

S. VALETTE

Radio Engineering

17 (June, 1937), No. 6

Retarding Undesired Emission in Vacuum Tubes (p. 7). B. H. PORTER
Recent Tube Developments (p. 13).
Distortion in High-Fidelity Audio Amplifiers (p. 16). R. LEE

FALL, 1937, CONVENTION

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA, NEW YORK
OCTOBER llth-14th, INCLUSIVE

Officers and Committees in Charge

W. C. KUNZMANN, Convention Vice-President

J. I. CRABTREE, Editorial Vice-President

S. K. WOLF, President

O. M. GLUNT, Financial Vice-President

G. E. MATTHEWS, Chairman, Papers Committee

G. FRIEDL, Chairman, Atlantic Coast Section

Local Arrangements and Reception Committee

G. FRIEDL, JR., Chairman

O. M. GLUNT A. S. DICKINSON E. A. WILLIFORD

H. B. SANTEE M. C. BATSEL E. G. HINES

A. N. GOLDSMITH H. RUBIN V. B. SEASE

L. W. DAVEE T. RAMSAYE D. E. HYNDMAN

E. I. SPONABLE O. F. NEU J. A. NORLING

Registration and Information

W. C. KUNZMANN, Chairman
E. R. GEIB S. HARRIS F. HOHMEISTER

Ladies' Reception Committee

MRS. S. K. WOLF and MRS. O. F. NEU, Hostesses
MRS. O. M. GLUNT MRS. T. E. SHEA MRS. A. S. DICKINSON

MRS. H. GRIFFIN MRS. J. FRANK, JR. MRS. E. A. WILLIFORD

MRS. E. I. SPONABLE MRS. G. FRIEDL, JR. MRS. M. C. BATSEL

Banquet Committee

A. S. DICKINSON, Chairman

O. M. GLUNT W. C. KUNZMANN H. GRIFFIN

J. H. SPRAY S. HARRIS O. F. NEU

G. FRIEDL, JR. M. C. BATSEL H. B. SANTEE

Publicity Committee

W. WHITMORE, Chairman

J. J. FINN G. E. MATTHEWS -F. H. RICHARDSON

J. R. CAMERON S. HARRIS P. A. McGumE

224

FALL CONVENTION 225

Projection Committee

H. GRIFFIN, Chairman

H. RUBIN F. E. CAHILL, JR. G. C. EDWARDS

J. O. BAKER M. D. O'BRIEN A. L. RAVEN

P. D. RIES J. S. WARD C. F. HORSTMAN

C. R. WOOD
Officers and Members of New York Projectionists Local 306, I. A. T.S. E.

Membership Committee

E. R. GEIB, Chairman

S. HARRIS A. A. COOK J. A. MILLER

J. A. HAMMOND J. K. ELDERKIN J. R. MANNHEIMER

Hotel Accommodations

O. F. NEU, Chairman

P. A. McGuiRE M. W. PALMER J. H. KURLANDER

D. E. HYNDMAN J. J. FINN P. D. RIES

Headquarters

The headquarters of the Convention will be the Pennsylvania Hotel, where ex-
cellent accommodations have been assured and a reception suite will be provided
for the Ladies' Committee. An excellent program of entertainment will be ar-
ranged by the hostesses.

Special hotel rates guaranteed to SMPE delegates, European plan, will be
as follows:

One person, room and bath $3 . 50
Two persons, double bed and bath 5 . 00

Two persons, twin beds and bath 6 . 00

Parlor suite, one person 11 .00 up

Parlor suite, two persons 13. 00 up

Room reservation cards will be mailed to the membership of the Society in the
near future, and everyone who plans to attend the Convention should return his
card to the Hotel promptly in order to be assured of satisfactory accommodations.
Consult your local railroad ticket agent with regard to coach and pullman rates.

Parking accommodations will be available to those who motor to the Conven-
tion at the fire-proof garage of the Hotel, at the rate of $1 .25 for twenty-four hours
or $1.00 for twelve hours, including pick-up and delivery at the door of the Hotel;
weekly rate, $7.50.

Technical Sessions

An attractive program of technical papers and presentations is being arranged
by the Papers Committee. All technical sessions, apparatus symposiums, and
film programs will be held in the Salle Moderne of the Hotel, on the eighteenth
floor.

There will be no general Apparatus Exhibit, but those who have developed new
equipment during the past year are invited to submit technical descriptions of it
to the Papers Committee for possible inclusion in the Apparatus Symposium.

226 FALL CONVENTION

Registration

Registration headquarters will be located on the eighteenth floor of the Hotel at
the entrance of the Salle Moderne, where the technical sessions will be held. Ex-
press elevators from the lobby will be reserved for the Convention. All members
and guests attending the Convention are expected to register and receive their
badges and identification cards required for admission to certain evening sessions
of the Convention, as well as to various de luxe motion picture theaters that will
honor the cards as courtesy admissions.

•Luncheon and Banquet

The usual informal get-together luncheon will be held at noon on October llth
in the Roof Garden of the Hotel, and the semi-annual banquet and dance will
take place on the evening of October 13th.

Addresses will be delivered by prominent members of the industry on both
occasions. At the banquet the annual presentation of the SMPE Progress Medal
and the Journal Award will be made, and the officers-elect for 1938 will be intro-
duced. The banquet will conclude with dancing and entertainment.

Tickets for admission to the informal luncheon and the banquet may be ob-
tained at the registration desk. Banquet tables reserved for 8, 10, and 12 per-
sons.

Ladies' Program

An especially attractive program for the ladies attending the Convention is
being arranged by Mrs. S. K. Wolf and Mrs. O. F. Neu, Hostesses, and the Ladies'
Committee.

A suite will be provided at the Hotel, where the ladies will register and meet for
the various events on their program. Further details will be published in a suc-
ceeding issue of the JOURNAL.

Entertainment and Diversion

Golfing privileges may be arranged at several country clubs in the vicinity of
New York, as well as various tours to points of interest in and about the city.
These arrangements may be made either at the Convention registration desk or
through the management of the Hotel.

SOCIETY ANNOUNCEMENTS

BOARD OF GOVERNORS

At a meeting held at the Hotel Pennsylvania, New York, N. Y., on July 9th,
nominations of officers for 1938 were completed by the Board of Governors.
Announcement of the nominees will be made as soon as all the acceptances have
been received. Ballots will be mailed to the voting membership on or about
September 2nd, and the results of the election will be announced at the Fall Con-
vention on October llth. The officers-elect will assume office on January 1st.

The report of finances submitted by Mr. O. M. Glunt, Financial Vice-President,
indicated that although conditions were satisfactory, quite a number of members
have not yet paid their 1937 dues. A third dues notice is being mailed to each
delinquent member at the time this issue goes to press, and all who have not paid
their dues so far are urged to do so immediately.

Committees and other details relating to the approaching Fall Convention, as
described in the preceding section of this issue of the JOURNAL, were announced
by Mr. W. C. Kunzmann, Convention Vice-President, and arrangements are being
made to gather an interesting selection of technical papers and presentations
under the direction of Mr. J. I. Crabtree, Editorial Vice-President.

SMPE TEST-FILMS

A new negative has just been completed for the 35-mm. sound test -film, re-
corded by the ultraviolet-light system. The contents of the film are identical with
those of the preceding negative, except that new and more appropriate musical
selections and voices have been chosen. The test-film was originally described in
the August, 1933, issue of the JOURNAL, p. 89. Some details of the contents of
the films are given in the advertisement on a following page.

In addition, a 16-mm. sound test-film has been prepared, the contents being
identical with those of the 35-mm. sound test -film, except that the frequency range
and the series of fixed frequencies extend to 6000 cycles instead of to 10,000.

The complete set of test-films available at the prices stated is as follows :

(1) 35-mm. sound test-film $37.50

(2) 35-mm. visual test-film 37.50
(5) 16-mm. sound test-film 25.00
(4) 16-mm. visual test-film (optical reduction of the 35-mm. visual

test-film) 25.00

ADMISSIONS COMMITTEE

At a recent meeting of the Admissions Committee, at the General Office of the
Society, the following applicants for membership were admitted to the Associate
grade :

227

228

SOCIETY ANNOUNCEMENTS

[J. S. M. P. E.

ALAG, S. S.

Murtiza Pore (Berar),

India.

ALSDORF, S.
P. O. Box 63,

North Hollywood, Calif.
ANDERSON, C. P.
706 W. Grand Ave.,

Oklahoma City, Okla.
ASHTON, T.

831 N. Rose Ave.,
Burbank, Calif.
BANCHINI, A.
Via Saturnia, 29,

Rome.
BARRETT, C. H.

5228 De Lonpre Ave.,

Hollywood, Calif.
BLANEY, A. C.

RCA Manufacturing Co., Inc.,
1016 N. Sycamore Ave.,
Hollywood, Calif.
CLARK, J R., JR.
2468 Lyric Ave.,

Los Angeles, Calif.
COMYUS, W. L.
1646 S. Olive St.,

Los Angeles, Calif.
DAVIS, F. W.
231 Clinton Heights Ave.,
Columbus, Ohio.

DlLAURO, J. J. »

5611 Carlton Way,
Hollywood, Calif.
DORSEY, G. H.
645 N. Martel,

Hollywood, Calif.
HAMILTON, E. W.
1216 Burrard St.,

Vancouver, B. C.
Hawkins, J. N. A.
2807 Eighth Ave.,

Los Angeles, Calif.
HEATH, G. M.

24 Murriverie Road,
North Bondi,
New South Wales,
Australia.

HOLMQUIST, J. G.
1935 Del Mar Ave.,

Wilmar, Calif.
JACKSON, B. B.

24 East Newell Ave.,

Rutherford, N. J.
JONES, P. C.

7510 Claybeck Ave.,

Burbank, Calif.
KAPLAN, H. S.
305 Dundas St., W.,
Toronto, Ontario,
Canada.
KISSACK, R. A.

University of Minnesota,

Minneapolis, Minn.
KNETTLES, E. D.
10,820 Morrison St.,

North Hollywood, Calif.
KNUTSEN, H. H.

Hans H. Knutsen & Co.,
Munkedamsveien 35,
Oslo, Norway.
KUMMINS, D.

176 Clarkson Ave.,
Brooklyn, N. Y.
LAY, F. L.

1961 S. Vermont Ave.,

Los Angeles, Calif.
MORSE, L. R.

Studios and Laboratory,
179 Inverness,
P. O. Box 411,
Manila, P. I.
PARCE, C. W.
1343 N. Citrus,

Hollywood, Calif.
PILTZ, C. A.,
39 Oxford St.,

Newark, N. J.
RALKE, C. H.

604 N. Walden Drive,
Beverly Hills, Calif.
RAYMOND, R. L.

Technicolor Motion Picture Corp.
Drawer 791,
Hollywood, Calif.

Aug., 1937]

SOCIETY ANNOUNCEMENTS

229

RETTINGER, M.
1438 E. 18th St.,

Los Angeles, Calif.
RICCI, E.

Calle F. Lacroze 2176,

Buenos Aires, Argentina.
SANDERSON, J.

824V2 N. Las Palmas Ave.,

Hollywood, Calif.
SCHMIDT, R.

Afifa, Viktoriastrasse,
Tempelhof,
Berlin, Germany.
SMITH, H.

Smith Theatre Supply,
617 First Ave.,
Spokane, Washington.
STARKE, H. A.

101 N. Kenmare Ave.,

Los Angeles, Calif.
STONE, R. L.

4207 Brighton Ave.,
Los Angeles, Calif.
TANSON, R. L.
243 Oakland Ave.,
Oakland, Calif.

UNDERGILL, C. M.

Batten, Barton, Durstine & Osborn,
383 Madison Ave.,
New York, N. Y.
VAN SLYKER, R.
5127 Eleventh Ave.,
Los Angeles, Calif.
WALKER, M. S.
16 Clifton Ave.,
Burwood,
New South Wales,
Australia.
WENDT, P. R.

4601 Sunset Blvd.,
Hollywood, Calif.
WILLIAMS, W. E.

845 South Manhattan Place,

Los Angeles, Calif.
WORK, L. P.

532 Fourth Ave.,
Clinton, Iowa.
ZALUSKEY, C. J.

6013 29th Ave., N. E.,
Seattle, Washington.
ZUCKER, F.

359 Ft. Washington Ave.,
New York, N. Y.

In addition, the following applicants have been admitted by vote of the Board
of Governors to the Fellowship (F) and Active (M) grades:

HARWELL, H. W. (F)
Cinaudagraph Corp.,
2 Selleck St.,
Stamford, Conn.
FRIEND, H. H. (F)
Cinaudagraph Corp.,
2 Selleck St.,
Stamford, Conn.
BOYER, M. R. (M)

Du Pont Film Mfg. Corp.,

Parlin, N. J.
GROSJEAN, G. M. (M)

Electrical Research Products, Inc.,
7046 Hollywood Blvd.,
Los Angeles, Calif.

HARPER, P. F. (M)

821 N. Poinsettia Place,

Hollywood, Calif.
NEUSCHOTZ, R. (M)
General Delivery,

Los Angeles, Calif.
PEARSON, L. C. (M)

Dominion Sound Equipments Ltd.
1620 Notre Dame St.,
W. Montreal,
Quebec, Canada.
THOMAS, C. (M)

Hollywood Camera Exchange,
1600 Cahuenga Blvd.,
Hollywood, Calif.

S. M. P. E.

STANDARD TEST-FILMS

These films have been prepared under the supervision of the Projection
Practice Committee of the Society of Motion Picture Engineers, and are
designed to be used as precision instruments in theaters, review rooms,
exchanges, laboratories, factories, and the like for testing the perform-
ance of projectors.

Only complete reels, as described below, are available (no short sections
or single frequencies). The prices given include shipping charges to all
points within the United States ; shipping charges to other countries are
additional.

35-Mm. Sound-Film

Approximately 500 feet long, consisting of recordings of several speak-
ing voices, piano, and orchestra; buzz- track; fixed frequencies for focus-
ing sound optical system; fixed frequencies at constant level, for de-
termining reproducer characteristics, frequency range, flutter, sound-
track adjustment, 60- or 96-cycle modulation, etc.

The recorded frequency range of the voice and music extends to 10,000
cps. ; the constant-amplitude frequencies are in 15 steps from 50 cps. to
10,000 cps.

Price $37.50 each, including instructions.

35-Mm. Visual Film

Approximately 500 feet long, consisting of special targets with the aid
of which travel-ghost, marginal and radial lens aberrations, definition,
picture jump, and film weave may be detected and corrected.

Price $37.50 each, including instructions.

16-Mm. Sound-Film

Approximately 400 feet long; contents identical to those of the 35-mm.
sound-film, with the exception that the recorded frequency range ex-
tends to 6000 cps., and the constant-amplitude frequencies are in 11
steps from 50 cps. to 6000 cps.

Price $25.00 each, including instructions.

16-Mm. Visual Film

An optical reduction of the 35-mm. visual test-film, identical as to
contents and approximately 400 feet long.
Price $25.00 each, including instructions.

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA

NEW YORK, N. Y.

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX SEPTEMBER, 1937 Number 3

CONTENTS

Page

Recent Progress in Acoustics V. O. KNUDSEN 233

The New Agfacolor Process. . . J. L. FORREST AND F. M. WING 248
The RCA Recording System and Its Adaptation to Various

Types of Sound-Track G. L. DIMMICK 258

A Device for Direct Reproduction from Variable- Density Sound

Negatives W. J. ALBERSHEIM 274

An Automatic Sound-Track Editing Machine G. M. BEST 281

A Dubbing Rehearsal Channel H. G. TASKER 286

The Evolution of Special-Effects Cinematography from an

Engineering Viewpoint F. W. JACKMAN 293

Present Aspects in the Development of 16-Mm. Sound

A. SHAPIRO 303
New Motion Picture Apparatus

Improved Noise-Reduction System for High-Fidelity Re-
cording

H. J. HASBROUCK, J. O. BAKER, AND C. N. BATSEL 310

Two New Films for Duplicating Work

C. E. IVES AND J. I. CRABTREE 317

Infrared Negative as Applied to Special-Effects Photography

G. W. HOUGH AND W. LEAHY 326

Current Literature 330

Book Review 332

Committees 334

Fall, 1937, Convention; Hotel Pennsylvania, New York, N. Y.,

October ll-14th 339

Society Announcements 343

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS, EDITOR

Board of Editors
J. I. CRABTREE, Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum; to members, $5.00 per annum,
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y.
Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers in question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 100 E. 42nd St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 463 West St., New York. N. Y.
Convention Vice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK, JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York, N. Y.

GOVERNORS

M. C. BATSEL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 25 Hunter Ave., Fanwood, N. J.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE, 205 W. Wacker Drive, Chicago, 111.

RECENT PROGRESS IN ACOUSTICS*
V. O. KNUDSEN**

Summary. — Some recent developments in acoustics, especially in Germany,
Russia, and in the author's laboratory, are reviewed. Experiments by E. Meyer,
of Berlin, help to clarify the differences between geometrical and diffuse reflections
of sound in rooms, and reveal the nature of some of the errors inherent in reverbera-
tion measurements. Meyer also describes special absorbent materials, as thin wood
panelling or stretched oilcloth, which are selectively absorbent for low frequencies.
S. Rschevkin, of Moscow, describes a method for prolonging, diminishing, or other-
wise modifying the reverberation in a room by means of Helmholtz resonators.

A new electrodcoustical device for the artificial production of vowels, by K. W.
Wagner, of Berlin, is capable of generating typical German vowels that can not be
distinguished from the originals. The oscillogram and sound spectrum of the arti-
ficial vowel resemble more closely the oscillogram and sound spectrum of the original
vowel than do two sets of oscillo grams and sound spectra of the same vowel "picked
up" at two different microphone positions in the same room. The experiments
reveal the nature of sound distortion caused by reflections from the boundaries of a
room, and show that the ear tolerates considerable distortion.

The paper concludes with a review of some recent work undertaken by the writer,
including resonance in rooms, the acoustical design of broadcasting studios, and
vistas in musical acoustics.

It is the purpose of this paper (a) to review some recent advances of
acoustics in foreign countries, and (b) to describe briefly some acous-
tical experiments now in progress at the University of California at
Los Angeles.

Acoustical research in Germany, especially as applied to buildings,
is largely concentrated in one place, the Institute for Vibration Re-
search, in Berlin. Much of this work has been done by E. Meyer and
his associates, under the direction of K. W. Wagner, the Director of
the Institute.

(I) MEASUREMENTS OF SOUND ABSORPTION COEFFICIENTS

Meyer1 has investigated the nature of the reflection of sound in
rooms by comparing the differences in the distribution of light in small

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received
May 26, 1937.

** University of California, Los Angeles, Calif.

233

234 V. O. KNUDSEN [j. S. M. p. E.

optical chambers for specular and for diffuse reflection from the
boundaries of the chamber. The calculation of the reverberation
time in rooms is based upon a theory that assumes diffuse reflection,
whereas the materials ordinarily used for the boundaries of a room
give rise to reflections that are chiefly "specular." Meyer made
measurements of the absorption of light inside a so-called "Ulbricht"
ball, which is an optical chamber with boundaries that reflect light
diffusely. It is not practicable to measure the "reverberation time"
for light in such a chamber, since the rate of decay of the light
is so very fast. However, it is practicable and relatively simple, to
measure the average intensity of light in the chamber, first when the
Ulbricht ball is empty, and afterwards with a certain area of absorp-
tive material (paper) inside the chamber. The theory of Ulbricht is
similar to that of Sabine or Eyring, that is, the total absorption of the
chamber is inversely proportional to the average intensity of light
within the chamber. Meyer reports that the absorption of the added
piece of paper was completely independent of the position of the piece
of paper inside the Ulbricht ball, but that the measured absorption of
the paper varied enormously when similar measurements were made
in a chamber that reflected light specularly. Meyer reports also that
the measured coefficient of absorption of the piece of paper was inde-
pendent of its size (the area varied in the ratio of one to one hundred) ,
as measured in the Ulbricht ball.

These results indicate that we should use reverberation chambers
with diffusely reflecting boundaries, if we expect to obtain reliable
coefficients of sound absorption by means of the reverberation equa-
tions that are commonly used in practice. Meyer has made acous-
tical measurements in the chamber shown in Fig. 1, and found that
the results of sound absorption measurements, at a frequency of
7000 cps., depended much less upon the position of the material, and
upon its size, than was the case when the boundaries of the chamber
were smooth. It is obvious, however, that it would be impracticable
to provide such chambers for low frequencies — even of the order of
100 cps., where the irregularities of the surface would have to be of
the order of ten to twenty feet.

For several years the writer and several of his pupils have investi-
gated the possibility of measuring sound absorption coefficients of
acoustical materials by using the intensity method instead of the de-
cay method. Using a constant source of sound in the chamber, the
average intensity of the steady state is measured first with the room

Sept., 1937]

PROGRESS IN ACOUSTICS

235

empty and then with the absorptive material in the room. In some
preliminary experiments it was found that the absorption coefficient
of Acousti-Celotex was essentially independent of the area of the
sample from an area of four square-feet up to an area of 144 square-
feet. The intensity method of measuring sound absorption involves
many difficulties in the technic of measurement, but both the theory
and the preliminary measurements indicate that we should be able to

FIG. 1. View of reverberation chamber with bound-
aries that reflect high-frequency sound (7000 cps.) dif-
fusely. (E. Meyer)

obtain more reliable coefficients of sound absorption by this method
than we can by the reverberation method.

(II) SOUND TRANSMISSION THROUGH DOUBLE PARTITIONS

Cammerer and Durhammer2 find that there is an optimal separa-
tion between double partitions, for the insulation of sound. Their
results are particularly applicable to the use of double windows be-
tween studios and monitor or control rooms. Fig. 2 shows the trans-
mission loss due to the air-space, as a function of the width of the air-
space between the two partitions, for a frequency that is the geomet-
rical mean of the frequency range of 100 to 3000 cps. It will be seen
that the optimal separation is ten centimeters. This, of course, ap-
plies for the frequency of 547 cps., that is, the geometrical mean of 100
and 3000. Meyer and others have shown that the transmission loss

236

V. O. KNUDSEN

[J. S. M. P. E.

can be increased by introducing absorptive material into the air-
space around the edges that separates the two partitions. This ab-
sorptive material increases the damping for any natural frequencies
or "eigentones" within the air-space, and thereby reduces the coup-
ling between the two partitions. If it is desired to obtain the optimal
transmission loss at frequencies lower that 547 cps., the separation of
the two partitions should be greater than ten centimeters. For fur-

6 8 10 12 W 16 18 20cm

FIG. 2. Sound insulation attributable to air-
space between double partitions, for a frequency
of 547 cps. (Cammerer and Durhammer)

ther details, the article by Cammerer and Durhammer should be
consulted.

(HI) TRANSMISSION OF SOUND THROUGH SMALL OPENINGS

It is not generally appreciated by acoustical engineers that a small
opening transmits very much more sound energy than would be cal-
culated upon the assumption that the total flux of energy through the
opening is equal to the product of the sound intensity / times the area
of the opening A . The actual flux of sound energy through the open-
ing is klA, where k is a constant that depends upon the size and shape
of the opening and upon the wavelength of the sound. Wintergerst
and Knecht, following the theory of Lord Rayleigh, have made mea-
surements of the transmission of sound through small circular and
rectangular openings. For a small circular aperture, of the order of
three to twelve millimeters in diameter, their measurements agree

Sept., 1937] PROGRESS IN ACOUSTICS 237

with the Rayleigh diffraction theory. • The results are given as
follows :

Frequency 100 200 400 800 1200 1600

k 75 56 29 12 6 2.5

For an opening 71 millimeters long, and of different widths as indi-
cated in the table, they obtained, at a frequency of 800 cps. :

Slit width (mm.) 0.1 0.2 0.5 1.0 2.0 3.0

k 300 200 100 64 38 33

The dependence of k upon the frequency is approximately the s. me for
rectangular openings as for circular apertures. These results are
significant to the acoustical engineer not only in sound insulation but
also in the design of sound absorbent materials — the excess of sound
energy transmitted through the openings is "absorbed" from the in-
cident sound-waves.

(IV) CONTROL OF REVERBERATION IN A ROOM BY MEANS OF RESONATORS

It is well known that the ancient Greeks attempted to improve the
acoustics of their open-air theaters by distributing a large number of
bronze vessels, fashioned into resonators, in regularly spaced niches
throughout the seating area of the theater. These resonators were
carefully tuned to respond to the various notes of musical systems
and thereby would emphasize the more important frequency com-
ponents of speech and music, and would particularly emphasize
those notes in music that correspond to the harmonic scale. It is not
improbable that these resonators would contribute some value to
speech and music, in emphasizing the particular frequency compo-
nents that are harmonious in music and contribute most to the intel-
ligibility of speech. Somewhat similar resonators, or sound-boxes,
are used in old Byzantine and Russian churches. Rschevkin3 has
treated theoretically this problem of resonators in rooms, and shows
that such a system of resonators in a room increases (1) the effective
volume of the room, and (2) the effective absorption of the room. If
the damping in the necks of the resonators is small, the volume effect
predominates, and the apparent reverberation time in the room is
increased especially for frequencies near the natural frequency or
frequencies of the resonators. If the absorption in the necks of the
resonators is large, the absorption effect predominates, and the appar-
ent reverberation time in the room is diminished for frequencies that
are near the natural frequency or frequencies of the resonators. By

238

V. O. KNUDSEN

[j. s. M. p. E.

means of such resonators it is possible to control the reverberation
characteristics of a room — especially to reduce the reverberation at
low frequencies, which is often desirable in studios treated with such
materials as porous or fibrous plasters, felts, tiles, etc. Rschevkin
tested this theory by placing eighty milk bottles upon the floor of a
small room. The apparent reverberation time was increased from
0.48 to 0.93 second for frequencies near the resonance frequencies of the

1 3 S T t H

FIG. 3. Oscillograms and sound spectra of the German vowel a spoken nine
times in succession by the same speaker. (K. W. Wagner)

bottles — about 230 cps. However, this prolonged reverberation was
due almost entirely to two rates of decay of sound in a room. The
decay during the first 30 db. was very little influenced by the resona-
tors, and it is this portion of the decay in rooms that is most signifi-
cant in determining the acoustical effects; only the latter part of the
decay was prolonged by the influence of the resonators. The observed
effects are explained upon the basis of a coupled system of room and
resonators. The bottle resonators had relatively little damping in

Sept., 1937] PROGRESS IN ACOUSTICS 239

the necks, and consequently their chief effect was to increase the re-
verberation time for frequencies near the resonance frequency of the
bottle, although at frequencies far removed from the resonance fre-
quency there was a small reduction in the measured reverberation
time in the room.

Rschevkin describes another form of resonator, made by one of his
colleagues, Astzifrov. These resonators consisted of circular disks of
plywood, fastened to the walls by means of a screw at the center.
The disks were 80 centimeters in diameter, and were held approxi-
mately three centimeters from the wall by means of a short piece of
wood through which the screw passed before it reached the wall.
These disks increased very appreciably the total absorption in the
room, although the effect was quite selective at the resonance fre-
quencies of the disks.

Similar resonance effects have been long observed in the cases of
furred-out plaster, wood sheathing, etc. For example, a half-inch of
acoustical plaster applied to a hard, rigid surface, such as concrete,
brick, or other masonry, has an absorption coefficient of only 0.08 to
0.10 at 128 cps. and increases to 0.30 or even higher, at high frequen-
cies; whereas this same plaster when applied to scratch and brown
coats over metal lath will give an almost uniform absorption over a
relatively wide range of frequency. It is quite probable that materials
of this type, utilizing the principles of flexural resonance, and an
appropriately designed network of pores in the absorptive material,
would result in an absorption characteristic that would be ideal for
controlling the reverberation characteristics in all rooms or studios.

(V) ARTIFICIAL PRODUCTION OF VOWELS

K. W. Wagner4 has developed a new electrical apparatus for the
artificial production of vowels. The apparatus consists of an impulse
oscillator that provides a wave-form very rich in harmonics, and a
series of five low-pass or band-pass filters in which the cut-off fre-
quencies and the sharpness of tuning can be controlled. A typical
German vowel is first analyzed into its frequency components. It is
then synthesized artificially by means of the apparatus just described.
It is possible artificially to produce vowels that are indistinguishable
from the originals after which they were modeled. There is a closer
resemblance between the original and artificial vowels than there is
between the same vowel spoken by the same person twice in succes-
sion, or between the same vowel as detected in two parts of a room by

240

V. O. KNUDSEN

[j. S. M. P. E.

high-quality recording apparatus. The oscillograms of typical Ger-
man vowels, and their frequency analyses, are among the best that
have yet been produced. The experiments reveal the nature of sound
distortion introduced by the acoustical properties of a room, such as
boundary reflection and resonance effects; they also show that the

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FIG. 4. Sound spectra of the same vowel, recorded
at three different positions in the same room. At top
is the spectrum of the input to the loud speaker. The
spectra at the left are for a large loud speaker; those
at the right for a small loud speaker. (K. W. Wagner)

ear tolerates considerable distortion, without detecting it.
4, and 5, reproduced from Wagner's article.)

(VI) RESONANCE IN ROOMS

(Figs. 3,

Some experiments the writer conducted in 1932 demonstrated that
reverberation consists of the damped free vibrations (or eigentones)
of a room.5 The frequencies n of the eigentones of a rectangular room
are given by the Rayleigh formula :

Sept., 1937]

PROGRESS IN ACOUSTICS

241

where c is the velocity of sound; /i, /s, and /3 are the dimensions of the
room; and p, q, and r are integers, 1, 2, 3, ... Both the steady-
state distribution of sound in a room and the nature of the free decay
of sound in that room are very much affected by these eigentones and
by the exact location and directional characteristics of the source of
sound in that room. Unfortunately, the formulas we ordinarily use
for calculating intensity distribution and reverberation do not take

590

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FIG. 5. Oscillograms and sound spectra of the German vowel i (top) and
its artificial reconstruction (bottom). (K. W. Wagner)

into account these pertinent properties, and as a result we find many
serious discrepancies between the calculated values of intensity dis-
tribution or reverberation and the observed values. For example,
the writer found that when the ceiling of a small room 8 by 8 by 9.5
feet, was covered with a highly absorptive material, the measured
time of reverberation at 512 cps. was 1.54 seconds; whereas the value
calculated by the usual reverberation formula was only 0.61 second.
The eigentones, which depended solely upon horizontal motion,
were only slightly damped by the absorptive material in the ceiling,
and consequently persisted for a much longer time than would be pre-
dicted by a formula based upon diffuse sound and boundaries of uni-

242

V. O. KNUDSEN

[J. S. M. p. E.

form absorptivity. By removing approximately two-thirds of the
absorptive material from the ceiling and applying it to two adjacent
walls, there was reasonably good agreement between calculated and
measured times of reverberation. In general, it is desirable to dis-
tribute the absorptive material in a room, especially in a small room,
so that the rate of decay will be approximately the same in all direc-
tions. This not only makes the measured reverberation approximate
the calculated value, but also contributes to better acoustics.

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FIG. 6. Distribution of sound pressure in a six-foot cubical chamber
excited by a tone of 162 cps. generated by a cone type loud speaker located
in one corner of the chamber. The chamber is vibrating in the gravest
mode involving all three dimensions. At top left is the distribution over
a plane one foot from one end of the chamber; top center is the plane two
feet from this end, etc.

The writer and two of his students, R. Neil and C. Hendrickson, have
investigated the intensity distribution of sound in a six-foot cubical
chamber at frequencies corresponding to several of the lowest eigen-
tones. For the gravest mode of vibration involving all three dimen-
sions, that is for p = q = r = I, in which case the frequency n is 162
cps. for the six-foot cubical chamber, the alternating pressure in the
sound-field is a maximum at (or very near) the boundaries of the
chamber and diminishes to zero (nearly) at the three planes that
divide the chamber into eight equal cubes. Fig. 6 exhibits the pres-
sure distribution over a series of six planes parallel to one wall of the

Sept., 1937] PROGRESS IN ACOUSTICS 243

chamber, and spaced one foot apart. Over the entire plane midway
between two opposite walls the pressure was practically reduced to
zero. For higher modes of vibration the sound-field will be more
complex, but each mode will be characterized by a definite geometrical
pattern of nodal and antinodal surfaces.

These resonance phenomena have more than academic interest;
they exist in all rooms and are responsible for many of the difficulties
that attend the placement of microphones in recording and broadcast-
ing studios. They are likely to be most troublesome in small, rever-
berant studios, and especially for low-pitched tones. For high-
pitched tones, that is, tones that have a short wavelength in compari-
son with the dimensions of the room, several contiguous eigentones
will be excited, and the overlapping patterns in the room will tend to
give a diffuse distribution of sound.

The acoustical engineer must gain a better knowledge of resonance
in rooms before he can understand and control the complicated phe-
nomena of intensity distribution and reverberation which are so inti-
mately related to room resonance.

(VII) MODERN ACOUSTICS AND MUSIC

In conclusion, the writer wishes to direct attention to a field of re-
search where science and art meet upon common and fertile ground.
Acoustics and music have enjoyed a long and intimate relationship,
although in recent years there has been a paucity of scientific workers
in the fields of both music and acoustics. Acoustics owes its origin to
the scientific study of music ; and acoustics is now in a position to re-
pay its debt to music. The motion picture and radio arts are in a
particularly favorable position to renew the development of music by
means of the applications of modern acoustics — and, the writer be-
lieves, much to the advantage of music as well as the motion picture
and radio arts.

Already the Bell Telephone Laboratories have developed the so-
called three-channel amplifying system, by means of which it is pos-
sible to preserve "auditory perspective" in the reproduced sound, or to
augment or diminish, at the will of the conductor, the loudness of the
sound coming from an entire orchestra, or from one or more sections of
the orchestra, and thus vary the apparent size and composition of an
orchestra of seventy-five persons as effectively as if there were two
thousand persons in the orchestra. Harvey Fletcher in collaboration
with Leopold Stokowski and the Philadelphia Orchestra already have

244 V. O. KNUDSEN [j. s. M. P. E.

given several demonstrations of new developments in music made
possible by this three-channel system. By employing more than
three channels, and associating low-pass, band-pass, or high-pass
filters with each channel, even greater versatility is made possible;
for example, any solo instrument or group of instruments in an orches-
tra (or in any other musical ensemble) can be amplified any desired
amount, and the tonal quality of the instruments associated with each
channel can be altered by suppressing or augmenting the low-,
medium-, or high-frequency components. Studios with variable and
controllable reverberation characteristics, or studios associated with a
reverberation chamber, can be used to produce musical effects that
would enhance the beauty and interest in many broadcasts or sound
recordings. These are only a few of the devices the radio and motion
picture arts may utilize in creating new musical experiences. Here is a
virgin field where the musician and acoustician, working together,
can make some noteworthy contributions to the radio and motion
picture arts.

Existing musical instruments are limited with regard to pitch and
loudness ranges, and especially with regard to tonal quality. Our
conventional musical instruments are capable of producing only a
small fraction of the almost infinitely many tonal qualities that are
possible. Electroacoustical instruments can be designed that are
capable not only of producing, but also of greatly extending, all the
frequencies, intensities, and tonal qualities of existing musical instru-
ments. Our present instruments began with varied arrangements
of bamboo, reeds, grass, tree stumps, skins, stones, plant and animal
fibers, gourds, wood, and metal — and, of course, the finest skills and
crafts of which man was capable. From these came the Boehm flute,
the Stradivarius violin, and the most elaborate of all instruments, the
pipe organ. The flute is, at least in respect of acoustics and me-
chanics, the most nearly perfected of these instruments, but it is limited
in its pitch range. The best violins, even when they are in tune, are
beset with unavoidable "wolf tones." Even our finest organs suffer
from the adventitious noise of rushing air and clanging action, and the
shorter pipes produce inharmonic as well as harmonic overtones. We
have been confined to the best that could 'be obtained from these per-
fected, but yet imperfect, instruments. Is there any reason to suppose
that the restricted ranges of pitch, loudness, and quality that these in-
struments supply are the most beautiful or expressive ones possible ?
Infinitely many varieties of tone-quality we have never sensed, and

Sept., 1937] PROGRESS IN ACOUSTICS 245

new extensions of the ranges of both pitch and loudness, are now pos-
sible by means of electroacoustical instruments. These instruments,
even if they should prove to be too expensive for personal ownership,
would contribute new life and interest to motion pictures, radio
broadcasting, and phonograph recordings. As composers became
familiar with the possibilities of such instruments they would be able
to create a new music which would be limited only by the im-
agination and creative ability of the composer. Research and devel-
opment are required to produce these instruments, but already several
electroacoustical instruments have been developed far enough to
indicate clearly the potentialities of such instruments.

The music of these new instruments, and all music of the future,
should be based not only upon the infinitely many tonal qualities
made possible by synthetic tones, but also upon the physical charac-
teristics of hearing, such as the dependence of auditory acuity upon
frequency ; the sensitivity of the ear to differences of intensity and fre-
quency; the masking effects of certain tones upon other tones; the
effects of auditory fatigue; the auditory reactions to contrapuntal
rhythms and melodies ; and the complicated relationships between the
subjective properties of pitch, loudness, and quality, and the objective
properties upon which they depend, namely, frequency, intensity, and
overtone structure. These are only a few of the physical character-
istics of hearing that should be regarded in creating the music and
musical instruments of the future. The musician, the psychologist,
and the esthetician are familiar with many other characteristics that
could and should guide future developments in music.

If the recently discovered characteristics of music and hearing had
been known to Helmholtz, and if the modern instruments of electro-
acoustics had been available in his time, music probably would have
gained much more than it did from his brilliant and comprehensive
studies of the physical nature of music. But we should not despair
that he left something useful for us to do. The time is now ripe for
repeating and extending these studies in a modernly equipped labora-
tory. Thus may we contribute to the raw materials from which there
will surely emerge a new and superior musical art, free from the imper-
fections inherent in existing musical instruments, and enhanced
with finer and more logical pitch and intensity gradations, more and
better tonal qualities, and more pleasing harmonies, rhythms, and
forms than man has yet experienced. Here, indeed, is a field where
the musician, the psychologist, the esthetician, and the acoustician

246 V. O. KNUDSEN [j. s. M. P. E

meet upon the same ground; where their joint efforts may lead to
new and glorious vistas in music; where acoustics, returning to its
exalted companionship with music, which called it into existence at
least twenty-five hundred years ago, may make its greatest contri-
bution to culture.

REFERENCES

1 MEYER, E.: J. Acoust, Soc. Amer., 8 (Mar., 1937), No. 3, p. 155.

2 Gesundheits-Ingenieur, Bd. 57, S. 556 (1934).

3 Technical Physics of the U. S. S. R., 3 (1936), p. 1.

4 Preussichen Akad. d. Wissenschaften, Phys.-Math. Klasse (1936), No. 2.

5 KNUDSEN, V. O. : "Resonance in Small Rooms," J. Acoust. Soc. Amer., IV
(July, 1932), No. 1, p. 20.

DISCUSSION

MR. KELLOGG: How much of a departure from a plain rectangular room do
you have to get before you break up the eigentones?

MR. KNUDSEN: I do not believe we can get rid of the eigentones in chambers
by means of non-parallel walls. Wherever boundary conditions are imposed
certain eigentones result. Of course, in the case of the rectangular chamber of
the type I discussed here where we had a cube, we would not get rid of the eigen-
tones simply by tilting the walls. There still would be eigentones, although
they would be much more difficult to compute.

MR. KELLOGG: Is the eigentone less pronounced with the oblong chamber?

MR. KNUDSEN: Yes, to a certain extent. When two dimensions are alike,
you get two eigentones that superimpose, so that certain eigentones are of greater
intensity. Eigentones depend not only upon the position of the source, but also
upon the directional characteristics of the source. In ordinary rooms and at
ordinary frequencies you excite not one eigentone, but usually ten, fifteen, or
even one hundred in some instances. At high frequencies, many eigen-
tones overlap, giving an even distribution of sound. At low frequencies and in
small rooms, we have to take into account the intensity distribution owing to
the eigentones; there is a definite distribution for each position and each
orientation of the source.

MR. HAWKINS: In the cubical room there would be set up one fundamental
eigentone many times the amplitude of the others, and probably most of the
others would be harmonics of that lowest one. What would be the difficulty in
damping the fundamental and the harmonics?

MR. KNUDSEN: Of course harmonics are present, but there are about ten
times as many others that are inharmonic. There are as many as thirty
eigentones per octave, and in many instances, some of the higher harmonics and
many of the inharmonic overtones would be excited. At the higher fre-
quencies they taper off quite rapidly, and the extent to which they do so is
governed by the damping of the room. If a room is very reverberant, a single
eigentone may be excited almost to the exclusion of -all others, especially at
low frequencies. If there is considerable damping in the room one single tone
excites a broader band of eigentones.

Sept., 1937] PROGRESS IN ACOUSTICS 247

MR. WOLF: The ability to get uniform response or uniform reverberation
has concerned us for a long time, and we have endeavored to determine whether
or not we wanted uniform reverberation both in the studio and the theater. Have
you any thoughts on what kind of characteristic is best for both the studio and
the theater?

MR. KNUDSEN: I have no new data. Two years ago, when I spoke to this
body, I referred to some experiments by Bekesy of Budapest, which, as far as
I know, are the most recent quantitative experiments. The experiments were
conducted in a radio broadcasting studio, for string quartet, solo singing, and
for piano, and led to a flat characteristic, flatter than in other experiments with
which I am acquainted.

MR. SKINNER: Have you ever speculated on what would happen if a room
were built in the shape of a horn? Would it eliminate any of the reverberation
and give a sound somewhat like the sound in a horn? It may be difficult to do,
but from a certain standpoint even a complete auditorium might be built in
such a fashion, if necessary, and eliminate many of the reverberations.

MR. KNUDSEN: Undoubtedly it would contribute much to eliminating the
eigentones and give a more uniform distribution.

MR. WOLF : Some time ago the principle was followed of letting every element
of a reproducing system have a flat characteristic, from the recording micro-
phones to the loud speakers in the theaters. The acoustical element, of course,
can certainly disturb the principle a great deal, and has. What are your opinions
on the subject?

MR. KNUDSEN: If you wish to reproduce speech and music with the same
loudness at which it was originally produced, then the answer would be, cate-
gorically, yes; but with respect to what is beautiful, what is desirable, I am not
sure that we are in a position to answer the question. The reverberation char-
acteristics are somewhat different from the characteristics of the electroacoustical
apparatus itself, and if you wish to simulate actual room conditions there may
be some necessity for having a reverberation characteristic other than a flat one.

My present recommendation with regard to reverberation in the studios is
that the reverberation time at 100 cps. be about 40 per cent longer than the re-
verberation time at 512 cps.; a flat characteristic from 512 to 4096 cps., and
probably a slightly rising characteristic at higher frequencies to compensate for
the very high attenuation of sound in the air. We are not ready to answer the
question completely, or, at least, I do not know just what the ultimate practice
will be.

THE NEW AGFACOLOR PROCESS*
J. L. FORREST AND F. M. WING**

Summary. — A survey of the history of monopack or multilayer photographic color
processes, including the methods of greatest importance at the present time: (a) silver
dye-bleaching methods and (b) silver dye-coupling methods. Silver dye-coupling
methods appear to be most promising, and have been successfully applied to monopack
films according to two distinct principles.

In one method, color-forming compounds are added to the developing solutions.
Color separation in this method depends upon control of the speed at which bleaching
solutions penetrate superposed emulsion layers. In the second method, employed in
the new Agfacolor process, the different color-forming substances, instead of being
added to the developing solution, are incorporated in emulsions coated in superposition
so that three differently colored images are simultaneously formed in a single develop-
ment. The metallic silver is subsequently removed by solvents leaving only pure dye.
images.

The process is based upon the pioneer work on color-forming methods of R. Fischer
who, before the World War, developed the process substantially as it is now being used.
The contributions to improving this process are the perfection of dyestuff -coupling
components better than those available to Fischer, improved methods of preventing
diffusion of the color-forming compounds, and methods of precisely controlling the
manufacture of multilayer film upon a large scale.

For many years before the time of Daguerre, users of the camera
obscura were familiar with the colored image thrown upon a focusing
screen. It is little wonder that with the advent of photography at-
tempts were made to record these colored images in the same manner,
and as simply as black-and-white photographs were made.

The evolution of the art, if we may so refer to it, has been slow
mainly because of the widely different methods by which the problem
has been attacked. It was soon discovered that the possibility of
finding a simple direct-color method was rather remote. This influ-
enced the trend of research toward more indirect methods of color re-
production. There, as before, no single path seemed to lead to the
objective. Many ways of reproducing color sprang up and flourished

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
June 24, 1937.

** Agfa Ansco Laboratories, Binghamton, N. Y.

248

NEW AGFACOLOR PROCESS 249

for a time, until in some cases insurmountable obstacles would ap-
pear, and indeed in most cases they did appear, and finally these ideas
became history. So great is the stimulation of interest in color photog-
raphy at this time, and so many very complete bibliographies of
color photography have been published, that it is not necessary to
discuss more than a very few of the methods that have shown the
most promise.

All these methods had one thing in common — a color analysis in
the neutral scale had first to be made. The color had to be analyzed
by breaking or dividing it into three components, as suggested by the
theory of Maxwell.1 Many very interesting and ingenious methods
of accomplishing this color analysis or separation have been proposed.

The most common way is to effect a separation by making three
exposures on panchromatic film through tricolor filters, and preparing
color positives from these separate negatives by any of the well known
procedures. This method is in general use today for still photog-
raphy, but for obvious reasons is unsuitable for exposures in rapid
succession, as for instance, motion pictures. Similar color separations
have been effected by the use of tripack and bipack films and plates.

It has been customary to classify the various color processes into
two groups — those that produce color by subtractive synthesis and
those that produce color by the additive method. The additive
methods are unexcelled in their simplicity and faithfulness of color
reproduction. However, because of the filters necessary for suc-
cessful operation, certain losses in light intensity result. Notwith-
standing this handicap, the Lumiere, Agfa, Finlay, and Dufaycolor
processes, based upon the additive principle, have proved very suc-
cessful for producing transparencies in color, the color separation
being effected by the use of a microscopic tricolor screen element
placed between the recording medium and the image. An ingenious
method was applied by Keller- Dorian-Berthon,2 and later made
available commercially under the names of Kodacolor and Agfacolor,
whereby the tricolor screen was placed in front of the optical system
of the camera and projector, and minute lenticular lenses were em-
bossed upon the back of the film. Technically there is a vast
difference between the reseau-based films and the lenticular films
using the optical filter system before the lens, but in some respects
the lenticular method may be regarded as a species of screen proc-
ess in which the filter elements are optically formed. Lenticular
and screen-plate additive methods are of interest because the processes

250 J. L. FORREST AND F. M. WING [J. s. M. p. E.

are simple to use, record all colors simultaneously and in exact register,
and can be processed simply, quickly, and inexpensively. However,
with both these systems the loss of light intensity is a major problem,
and, in addition, the production of duplicates has presented consider-
able difficulties when attempted on a commercial scale.

The desire for motion pictures in color has been a persistent and an
earnest one. Before the end of the past century proposals were
made for methods of producing motion pictures by the additive pro-
cess with a mechanical filter arrangement in both the camera and pro-
jector. It is interesting to note that at that time most experimenters
in the art seemed to give up hope of having a colored film. Efforts
were concentrated upon supplying the color from colored filters and
controlling the paths of light through the filters by black-and-white
film records. In 1897 such a method was proposed by Isensee.3 Both
the camera and the projector were equipped with rotating shutters
divided into three equal sectors holding the usual red, green, and
blue-violet filters through which successive pictures were exposed
and projected. Such processes depend upon persistence of vision to
fuse the successive images into a complete color picture. Numerous
additive processes belonging to the persistence-of-vision class have
been proposed and patented, and a few of the latter have been intro-
duced commercially. The most prominent was the Kinemacolor,
which flourished for several years before the World War. This was a
two-color method in which panchromatic film was exposed at twice
the normal speed behind a color-sector shutter so that alternate frames
were exposed behind red-orange and blue-green filters. A black-
and-white positive was printed in the usual manner, and projected
at double speed through a similar rotating color-filter on the pro-
jector. The rapid alternation between the red and green impressions,
which had to be integrated by the eye as the film was projected, led
to severe eye-strain. This, together with the additional cost for
film, proved objectionable. Additive persistence-of-vision methods,
although very old in principle, have appeared in recent years from
time to time as new workers in the art have striven to improve and to
put them into practical use, but none of these attempts at revival
have more than partially overcome the inherent disadvantages.

While persistence-of-vision methods were achieving a measure of
prominence, other experimenters were working on other additive
processes in which component pictures in two or more primary colors
were simultaneously projected in register upon the screen.

Sept., 1937] NEW AGFACOLOR PROCESS 251

Of the simultaneous-projection methods, the most prominent was
the three-color Gaumont process, which was capable of results beyond
criticism from the standpoint of quality. However, since the process
required special projection equipment, theater owners were reluctant
to purchase this equipment, for which an adequate supply of films
was not assured. This prevented any large measure of commercial
success.

When it was realized that any process of color cinematography re-
quiring special projection equipment was seriously limited from a
commercial standpoint, increased attention was given to methods for
producing films in which each frame was a complete color picture.
This led to the acceptance of subtractive methods and a decline of
interest in additive processes, with the exception of the screen-plate
and lenticular methods, which have alone survived.

Subtractive methods using bipack negatives and double-coated
positive films have become widely known. In some cases the color
was produced by inorganic toning, dye toning, or a combination of
both. In some of the three-color processes the third color, usually
the yellow, was applied by imbibition.

The well known Technicolor method, which has been widely
adopted commercially, is an outstanding achievement in a subtractive
color process. In this process tricolor separation negatives have to
be made, from which a transparent print in colors is produced using
the subtractive colors.

Of the various methods of color photography that have survived
none is free from limitations that prevent wide and general adoption,
nor is there any indication of the direction in which further improve-
ments of a fundamental nature could be made.

Because they represented the one branch of the art that gave some
hope of a brilliant future, the multilayer-film methods have finally
emerged into prominence after a long period of comparative obscur-
ity. These methods are characterized by the use of a film having
three differently sensitized emulsion layers coated in superposition
upon a single support, with screening dyes added to the emulsions,
or with interposed filter layers of dyed gelatin to assist in proper color
separation. The principle is clearly that of the familiar tripack,
which is the simplest form of tricolor separation, but the three emul-
sions are coated upon one another to form a single integral unit — in-
stead of the three separate films of the tripack. It is this class of
multilayer process and its history that are of chief concern.

252 J. L. FORREST AND F. M. WING [J. S. M. P. E.

The evolution of the multilayer film began well back in the past
century.4 In 1899 Selle divided a single sensitized layer into zones
of color-sensitivity by controlling the penetration of color-sensitizers
into the layer for various parts of the spectrum.

Controlled diffusion, though not described by this name, was em-
ployed by Wolff-Heide5 in the production of a multilayer color-film
process in which two layers of different color-sensitivity are provided
in one single coating. The Wolff-Heide process is a method of color-
ing images lying at different depths in one emulsion layer after the
emulsion has been sensitized according to the methods originated by
Selle.

One of the first suggestions for a multilayer coating was made
about 1905 by Schinzel,6 who suggested a process called Katachromie.
This was an outgrowth of the tripack principle, but the emulsion
layers were coated in superposition, each layer being sensitized to re
cord one of the tricolor components of the spectrum, and the layer it-
self dyed the complement of its color-sensitivity. The film was proc-
essed by a decolorizing method that decolorized the dyes in the re-
gions where metallic silver was formed by the exposure and develop-
ment. In this way a subtractive color picture could be formed by
this multilayer film. Although correct in theory, so many difficulties
presented themselves in applying the method that it never achieved
commercial acceptance. Further investigations along this line were
made by Heymer in 1927 in the Agfa laboratories.

Caspar also proposed three properly sensitized emulsion layers,
each of which was dyed complementary to the color to which it was
sensitive.7 In order that the staining dye would not interfere, by
absorption, with the radiation that should be used to expose the
silver halides, Caspar proposed to shift the color-sensitivity of the
silver halides somewhat from the maximum absorption of the stain-
ing dye. In this manner he improved the speed of the film. How-
ever, means have not yet been found to make the combined film,
which already contained the actual colors, sufficiently fast for short
exposure such as would be required in the camera. Caspar's process
has been introduced commercially, but the multilayer film is used
only for positive prints, and the usual three-color separation negatives
are required. Thus the silver dye bleaching method has become an
intermediate step in the transition from the older methods of indirect
photography to the modern multilayer process.

Another important development in color photography as it is now

Sept., 1937] NEW AGFACOLOR PROCESS 253

applied in multilayer films was the work of R. Fischer,8 and R. Fischer
and H. Siegrist,9 along the line of color development; that is, the for-
mation of colors in the film during its development. This advance
provided a new bridge between tricolor separations in terms of silver
and their translation into dye images. Fischer's work grew out of
early and preliminary discoveries of Homolka,10 Schinzel, Luther,11
Sforza,12 and others. Fischer applied this principle of color develop-
ment in a comprehensive manner to tricolor photography, and in
patents and publications provided a rather complete disclosure, not
only of the principle of color development, but the application of the
principle to multilayer films.

In addition, Fischer early9 included the use of specific developers
for this purpose, such as paraphenylenediamine, or its derivatives,
and many color-coupling components that could be incorporated in
the sensitive emulsion layers of a multilayer film, and which would

eniitivt layer with a yellow dye component,
yellow titter layer

Green sensitive layer with a rnasenta dye component.
Red sensitive layer with a cyan dye component.
Filrn base.

FIG. 1. Cross-section of the film.

provide upon development the proper subtractive colors with the
same developer.

Out of this long and active history of color photography, punctu-
ated by many failures and recorded by a great volume of patents and
publications throughout the world, there have emerged but few
color processes that have achieved any real measure of commercial
acceptance. Of these, the Technicolor process has been mentioned.
Reference should also be made to the Kodachrome film of the East-
man Kodak Company. This film and process have been previously
described, in detail. Suffice it to say here briefly that this film is of
the multilayer type capable of exposure in an ordinary camera, and
produces three black-and-white color-separation latent images simul-
taneously. By an ingeniously devised controlled-diffusion develop-
ing process carried on in the processing laboratory, each of the separa-
tion images is converted into the proper dye image.

The new Agfacolor film is a multilayer film, likewise capable of
simple exposure in an ordinary camera for the simultaneous formation

254

J. L. FORREST AND F. M. WING

[J. S. M. P. E.

of color-separation images, and is distinguished by the simplified
method with which it is processed to provide simultaneously the
color-images of the black-and-white records with one color develop-
ment.

The discovery of more powerful and more selective sensitizing
dyes; the improvement and perfection of substances for preventing
diffusion in and between the layers; the advances in the manufacture
of photographic emulsions and sensitized materials and methods of
coating them, together with the progress of the industry in the manu-

SUBJECT

LAYER
SENSITIVITY

COLOR OEV.

I.DEVELOPMENT COLOP-DEVELOPMENT

FIG. 2. Simultaneous formation of three color
records upon exposure.

facture of synthetic organic dyes, have made it possible for the Agfa
Laboratories to produce such a simplified multilayer film and process.
The new Agfacolor film (Fig. 1) comprises a single unitary film
structure consisting of a support or base upon which is coated in thin
superimposed layers three light-sensitive silver halide emulsions,
each made particularly sensitive to one of the primary colors. These
sensitive layers are arranged on the base in the following order: the
lowermost layer, i.e., next to the base, is sensitized for red light; the
next or middle layer is sensitized for green light; the top layer is sen-
sitized for blue light. Separating the sensitized coatings from each
other are yellow filter layers, the color of which disappears during

Sept., 1937]

NEW AGFACOLOR PROCESS

255

developing. The sensitive emulsion layers contain no dyestuffs but
do contain certain clear and colorless dyestuff-coupling components
which in subsequent treatment of the film produce colors in the
layers.

By exposing such a film to a colored object (Fig. 2) there will
be recorded simultaneously three separate color records, each sen-
sitized layer recording the image to which it is color-sensitive. The
color formation is brought about by the development of the film.
The particular developing substance in the developer oxidizes in

COLOR
DEVELOPMENT

3.

REMOVAL OF
THE SILVER

PICTURE-

SILVER HALIDE LATENT IMAGE DEV. SILVER

FIG. 3. Effects upon development.

those places where the exposed silver halide in the layer is reduced to
metallic silver. This oxidized developing substance couples with
the coupling components incorporated in the emulsion layers, and
forms in each layer the insoluble sub tractive color in proportion to
the silver that is reduced. The coupling compounds incorporated
in the three emulsion layers have such characteristics as to produce a
color in each layer that is complementary to the color for which the
layer is sensitized. Therefore, the color formed in the top or blue-
sensitive layer is yellow; the color formed in the middle or green-
sensitive layer is magenta ; and the color that is formed in the bottom
or red-sensitive layer is cyan. The colors formed in the layers re-

256 J. L. FORREST AND F. M. WING [J. S. M. p. E.

main in their respective positions and do not spread or diffuse from
one layer to the next. In addition, the colors are fast and are not
affected by the action of the processing solutions. In practice the
film is exposed in an ordinary camera. By this exposure there are
formed in the three emulsion layers latent images or color-sensation
recordings in accordance with the color-sensitivity of each layer; i.e.,
the blue of the subject will be recorded in the top layer, the green
of the subject will be recorded in the middle layer, and the red of the
subject will be recorded in the bottom layer. The film is now de-
veloped to form a black-and-white negative. The developer used
is an ordinary developer that does not form coupling oxidation prod-
ucts (Fig. 3). This prevents the formation of colors at this stage.
After exposure to white light, the remaining silver halides are de-
veloped in a developer of the para-Phenylenediamine type, the oxi-
dation products of which couple with the dye component in each of
the layers and form the subtractive colors in proportion to the metal-
lic silver that is reduced.

After this development, the film contains in the layers both the
metallic silver and the dyes. The silver is now bleached out with a
reducer, leaving alone in the layers the three superimposed pure dye
images, which give an accurate reproduction of the colors in the
original subject. The images are highly transparent and exception-
ally well suited for projection. Because of the absence of silver
grains, even larger-sized images may be projected than is customary
with black-and-white film.

Agfacolor film has been made available in Europe in the 35-mm.
width for miniature cameras and will be available shortly for
amateur motion pictures. It is expected that it will be marketed in
this country.

The motion picture industry, of course, will be interested in the
possibilities that this process may offer in the field of 35-mm. motion
pictures. Definite advances have been made in this direction, with
every indication pointing to a practical commercial application to
this wider field.

REFERENCES

1 WALL, E. J. : "History of Three-Color Photography," p. 2.
* U. S. Patent 992,151.

3 German Patent 334,776.

4 WALL, E. J.: "History of Three-Color Photography," p. 162.
6 Ibid., p. 164.

Sept., 1937] NEW AGFACOLOR PROCESS 257

« Brit. J. Phot., 1905.

7 Zeitschr. wissensch. Phot., 34, p. 119.

8 U. S. Patent 1,055,155 (1913).

9 Photographische Korrespondenz (1914), No. 640, p. 18; No. 644, p. 208.

10 Ibid. (1907), p. 55.

11 German Patent 396,485.

12 Phot. Coul. (1909).

DISCUSSION

MR. COOPER: Why is the separating layer between the green-sensitive emul-
sion and the red-sensitive emulsion dyed yellow? Should it not be dyed reddish?

MR. FORREST: The lowermost or red-sensitive layer is not green-sensitive.
Therefore, a reddish filter layer is unnecessary.

MR. KELLER: Do I understand correctly that the same color developer will
transform each of the color-separation layers to a different subtractive color?

MR. FORREST: Yes. The dye components in each layer are different, so that
one color developer will produce in each of the three layers one of the subtractive
colors; i.e., a yellow color will be formed in the top layer, a magenta color will be
formed in the center layer, and a blue-green or cyan color will be formed in the
lowermost layer.

MR. TOWNSLEY: Mr. Forrest, what is the effect of overexposure ?

MR. FORREST: Color-films are naturally more sensitive to the effect of incorrect
exposure than are black-and-white films. This is not due so much to the de-
creased latitude of color-films, but rather to the fact that variations in exposure
disturb the color balance. Incorrect exposure in the black-and-white scale also
interferes with the tonal reproduction. However, in the black-and-white film
the tones still remain in the gray scale; whereas in the case of the color-film, vari-
ous color tones result, and variation in color is much more quickly detected than
are variations in the neutral scale. Consequently, one has to be much more care-
ful in the exposure of all types of color-film than with black-and-white.

MR. CECCARINI: Do the three layers have identical gradation?

MR. FORREST: It is desirable that they should have for maximum latitude, and
as nearly as possible they do have the same gradation. However, the three color
characteristic curves can not be exactly the same.

MR. OFFENHAUSER: What is the difference in recording sound on Agfacolor
film with ultraviolet, as against recording with white light?

MR. FORREST: It is too soon to make a definite statement in regard to sound re-
cording on Agfacolor film. However, it will be necessary to use light that will
penetrate the three layers in order to produce a satisfactory sound-track.

THE RCA RECORDING SYSTEM AND ITS ADAPTATION TO
VARIOUS TYPES OF SOUND-TRACK*

G. L. DIMMICK**

Summary. — The photographic recording of sound is accomplished by modulating
a narrow beam of light and projecting it upon a strip of moving film. There are
three ways in which the amount of exposing light may be varied. A light-beam of
fixed dimensions may have its intensity varied; a beam of constant intensity and
length may have its width varied; or a beam of constant intensity and width may have
its length varied. The first two types of modulation produce variable-density sound-
tracks, while the third type produces variable-width tracks.

The recording optical system can be made to modulate either the intensity or the
length of the light-beam. The unit consists essentially of an incandescent lamp to
produce the light, a system of lenses to direct the light, an aperture and slit to limit
the light, and a reflecting mirror galvanometer to modulate the light. A magnetic
shutter for ground-noise reduction is also part of the standard variable-width re-
cording unit. A system of mirrors and lenses intercepts a small portion of the re-
cording light and projects it upon an external card. This system magnifies the
deflection of the galvanometer and shutter to such extent that the degree of modulation
and the zero settings can be observed easily by the unaided eye.

Many different types of sound-track can be made uith the recording optical system
without sacrificing any of its advantages as a light modulator. By the use of the
appropriate condenser and aperture assembly, the system will record standard bi-
lateral variable-width track, standard variable-density track, push-pull class B
variable-width track, push-pull class A variable-density track, and push-pull class
A variable-width track. The manner in which each of these systems functions is
shown and described in detail.

The photographic recording of sound is accomplished by modulat-
ing a narrow beam of light and projecting it upon a strip of moving
film. There are three ways in which the amount of exposing light
may be varied. A light- beam of fixed dimensions may have its in-
tensity varied; a beam of constant intensity and length may have
its width varied ; or a beam of constant intensity and width may have
its length varied. The first two types of modulation produce vari-
able-density sound-tracks, while the third type produces variable-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
June 15, 1937.

** RCA Manufacturing Co., Camden, N. J.

258

RCA RECORDING SYSTEM

259

width tracks.1 It is the object of this paper to describe the RCA
light-modulating system, to discuss some problems connected with
its design, and to show how it is adapted to record variable-width and
variable-density sound-tracks of various types.

The light-modulator consists essentially of an incandescent lamp
to produce the light, a system of lenses to direct the light, an aperture
and slit to limit the light, and a reflecting mirror galvanometer to
modulate the light. A magnetic shutter for ground-noise reduction
is also part of the variable-width recording unit. Fig. 1 shows the
optical layout. The image of the filament A is formed at the galva-
nometer mirror F by the combination of lenses, B and E, Most of the

FIG. 1. Optical system for variable- width recording.

power to form this image is in the condenser B. The intermediate
lens E has just sufficient power to form an image of the aperture C
upon the slit H. The condenser G forms an image of the mirror F
upon the objective lens J. The objective in turn forms an image of
the slit upon the film K. The filter / serves to restrict the radiant
energy to a narrow band in the ultraviolet. The two condensers, B
and G, and the two objectives, E and /, form a relay optical sys-
tem in which planes of non-uniform illumination appear at the fila-
ment, the galvanometer mirror, and the last objective, while planes of
uniform illumination appear at the aperture, the slit, and the film.
The lens mirror L is located immediately below the slit, and reflects
a corner of the recording light-beam for monitoring purposes. The
monitoring beam strikes the mirror N, is reflected vertically through
the lens 0 to the mirror M, which directs it to the monitoring card P.

260 G. L. DlMMICK [J. S. M. P. E.

An image of the galvanometer mirror F is produced at lens 0 by the
lens mirror L. The lens 0, in turn, forms an image of the plane H
upon the card. The action of the two monitoring mirrors, M and
N, is to rotate the planes of vibration through 90 degrees. Vibra-
tion of the galvanometer mirror in a vertical plane produces horizon-
tal vibration of the vertical edge of the triangular monitoring beam.
Horizontal motion of the shutter vanes D results in vertical motion
of the horizontal edge of the monitoring beam.

The Recording Lamp. — It is known from the laws of optics that if
we neglect the loss of light by reflection and absorption, the axial
illumination at the final image produced by any aplanatic system of
lenses depends only upon the brightness of the source of the solid
angle of the pencil of light converging to the center of the last image.
From this we conclude that the efficiency of the recording optical
system is independent of the size of the light-source, provided the
brightness of the source and the size of its image upon the galva-
nometer mirror are kept constant. There are other factors, however,
that determine the size of the recording lamp.

The life of an incandescent lamp depends, among other things, upon
the ratio of the volume to the surface area of the filament. Since the
volume varies as the square of the wire diameter and the surface area
varies directly as the diameter, it follows that the lamp life at a given
temperature increases with the wire diameter. The length of the
filament wire must be increased together with the diameter in order
to prevent excessive end-cooling. The coil length must be approxi-
mately twice the diameter so that the filament image can be made to
fill the galvanometer mirror in height, allowing the cooler end-turns
to fall off the mirror.

Other factors that favor a large light-source are the ease of lamp
adjustment, stability of the filament in operation, and the simplicity
of condenser design. If the filament is misaligned in a vertical plane
by an amount equal to its own diameter, the recording light is re-
duced to zero. A small-diameter source would require large magni-
fication, which would make it critical to adjust. Also the effects of
filament sag and mechanical vibration would be increased. The
speed required of the first condenser bears an inverse relation to the
source size. A single-element condenser can be used effectively only
if its speed does not exceed about f/2.

All these factors point to the desirability of a large light-source,
but there are limitations in this direction also. It is advantageous to

Sept., 1937] RCA RECORDING SYSTEM 261

keep the power requirements low, especially when the power is ob-
tained from storage batteries. The problems of lamp current con-
trol, lamp socket design, and heat dissipation grow very rapidly with
the size of the lamp. All things considered, the most satisfactory
light-source has been found in a lamp having a rating of 10 volts, 7.5
amperes. The filament helix has an outside diameter of 76 mils and
a length of 175 mils. The coil is slightly curved to improve the uni-
formity with which the aperture is illuminated and to increase the

FIG. 2. Curved filament: (a) front view;
(i) top view.

illumination obtained from the convex side at the expense of that ob-
tained from the concave side. The bulb is one inch in diameter and
is made of glass having a high transmission at 3650 A. Fig. 2 is an
enlarged photograph of the lighted filament. Fig. 3 shows how the
illumination varies with the angle for both the curved and the straight
filaments.

The Optics.2 — The intermediate lens E and the objective lens /,
(Fig. 1) are both achromats of the type largely used in microscopes.
They are so corrected as to bring the ultraviolet line (3650 A) and the
mercury green line (5461 A) to focus in the same plane. Like most

262

G. L. DlMMICK

[J. S. M. P. E.

microscope objectives, the correction for spherical aberration is
nearly perfect, and diffraction alone sets the limit of resolution. The
objective lens / has a focal length of 16-mm. and a numerical aperture
of 0.25. Maximum resolution of this lens is attained when the image
of the galvanometer mirror is about two-thirds the size of the lens

(feoxecsj

aperture,
equation

FIG. 3. Variation of illumination with angle for (a)
straight filament lamp; (b) curved filament lamp.

Under this condition, the resolving power is given by the

Z =

2(N.A.)

where Z is the smallest separation of two points, X is the
wavelength of the light, and N.A. is the full numerical aperture of the
lens. For a wavelength of 3650 A the objective is capable of resolving
two points separated by a distance of one thirty-fifth of a mil. It is
evident from this that no difficulty is experienced in projecting upon
the film a beam of light having a width of a quarter mil, or one-eighth
of the length of a wave on the film at 9000 cps. The size of the
mechanical slit is 1.9 mils by 570 mils, and the reduction ratio of the
objective is 7.5 to 1.

Condensers are not usually required to produce good images, but
their effectiveness in concentrating the light is increased as the aber-

>Sept., 1937]

RCA RECORDING SYSTEM

263

rations are reduced. Although it is not possible to eliminate spherical
aberration from a simple spherical lens, it may be minimized and
coma may be eliminated completely by choosing the radii so that the
deviation of the rays is divided equally between the two surfaces. In
designing the condensers for the recording optical system the rule of
equal deviation was adhered to. The lenses were made as thin as
possible to reduce absorption and the radii were chosen to give the
required focal length for a wavelength of 3650 A. Bausch & Lomb

FIG. 4. General construction of RCA photophone magnetic galvanometer.

spectacle crown glass was used because of its high transmission at
this wavelength.

The Recording Galvanometer. — The development of a large mirror
magnetic galvanometer3 (Fig. 4) presented many problems. One of
the most interesting of these and the last to submit to solution was
the problem of damping. The oscillograph galvanometers previously
used for sound recording obtained their damping from oil surround-
ing the ribbons and mirror. Although the damping properties of oil
are excellent, there are several reasons why its use in recording galva-
nometers is objectionable. The coefficient of damping varies over a
wide range with temperature. In order to obtain damping, it is neces-

264

G. L. DlMMICK

[J. S. M. P. E.

sary to move a considerable mass of oil. It is difficult to seal the gal-
vanometer sufficiently to prevent oil leakage.

The first dry galvanometers of the magnetic type were damped by
a pad of rubber surrounding the armature. By loading pure gum
rubber with tungsten powder, a high power-
factor, low temperature coefficient, and long
life were achieved. Although the method
provided sufficient damping at resonance it
did not prove successful for other reasons.
In addition to the required resistance, the
rubber supplied considerable stiffness and
mechanical hysteresis. But stiffness added
in this way is not reliable enough to be de-
pended upon for armature stability, so that a
loss of sensitivity resulted. Hysteresis is seri-
ous because it gives rise to a shifting zero
line.

The method of damping eventually adopted
makes use of the desirable properties of tungsten-loaded rubber, but
does not permit it to influence the low-frequency response of the
galvanometer. A cross-section taken through the armature and
damping assembly is shown in Fig. 5. Two small rectangular pieces
of tungsten-loaded rubber B are cemented to the armature A about

FIG. 5. Cross-
section of armature
and damping assem-
bly of galvanometer.

c,

FIG. 6. Electrical equivalent of damping assembly.

midway of its length. A bronze yoke C straddles the armature
and presses firmly against the outside faces of both pads. The metal
yoke does not touch the armature or the modulation coil surrounding
it. When the armature vibrates at low frequencies the yoke moves
with it and has no effect at all upon the stiffness. At high frequen-

Sept., 1937]

RCA RECORDING SYSTEM

265

cies, the inertia of the yoke causes it to stand still and the armature
vibrates inside it, compressing the rubber and damping the peak.

The electrical equivalent of the mechanical damping system is
given in Fig. 6. The mass of the armature and mirror is represented
by Li, while C\ represents the armature compliance. L2 represents
the mass of the yoke, Cz the compliance of the rubber, and r2 the ef-
fective resistance of the rubber. The resistance and reactance of the

-3

8= o.fr

&.
S.

0.1 1.0 10-0

FIG. 7. Resistance and reactance of damping assembly.

damping circuit has been determined from a mathematical analysis
of the equivalent circuit. Expressed in mechanical terms these are :

M2(l -

- 1

and - - =

+

X2 is the reactance of the damping assembly, 52 is the stiffness of the
rubber, Rz the resistance of the damping assembly, u the ratio of the
frequency in question to the resonance frequency of the damping
assembly, and B is the bluntness of the damping assembly as a res-
onator. The bluntness of a tuned mechanical vibrating system is
the ratio of the amplitude of deflection at low frequencies to the am-
plitude of deflection at resonance for a constant vibrating force. With
tungsten-loaded rubber as the damping material, the bluntness of the
damping assembly is 0.6. By placing this value in the two equations

266

G. L. DlMMICK

[J. S. M. P. E

above we may determine the relations between resistance, reactance,
and frequency. The curves in Fig. 7 show this relation. Values of
Xz/Si that are negative indicate mass reactance, while the positive
values indicate stiffness reactance.

The effect of the damping assembly upon the galvanometer charac-
teristic is shown in Fig. 8. The peak is reduced from 12 db. to about
3 db. The droop that occurs immediately before the peak is caused
by the inductance of the modulation winding. This can be overcome
and the frequency characteristic improved by placing a condenser

FIG. 8. Effect of damping upon galvanometer response: (broken curve)
damped; (solid curve) undamped.

across the biasing winding to neutralize the inductive reactance.
Its value may be chosen properly to boost the response where the
curve is lowest and to reduce the response at the peak. The effect
of bias capacitor upon galvanometer response is shown in Fig. 9.
The damping assembly is in place and constant voltage is applied to
the grid of the last tube. The effect of the bias capacitor upon the
impedance of the modulation winding is shown in Fig. 10.

Variable-Width Recording. — The vibrating-mirror system of light-
modulation is endowed with a high degree of flexibility. This flexi-
bility is made possible by the fact that the galvanometer does not
itself modulate the light, but rather imparts angular vibration to a
beam, the size and shape of which is determined by a stationary aper-

Sept., 1937]

RCA RECORDING SYSTEM

267

ture. The intersection of the vibrating beam with a narrow slit de-
termines the extent and form of the modulation. As shown in Fig.
11, variable- width sound-tracks may be produced either by making
the aperture rectangular in shape and vibrating its image across the
slit lengthwise, or by providing the aperture with one or more sloping
edges and vibrating its image at right angles to the slit length. The
second method is preferred because it enables us to record many types
of track that would otherwise be extremely difficult if not impossible.
If the aperture has more than one sloping edge or if the value of the
slope is less than unity, the sensitivity of the modulator is increased

FIG. 9. Effect of bias condenser upon galvanometer response : (broken
curve) no bias condenser; (solid curve) 0.035 /^f across biasing winding.

in direct proportion to the number of sloping edges and in inverse
proportion to the value of the slope. In case the objective is not
filled with an image of the galvanometer mirror, the advantage
of multiple sloping edges may be utilized to increase the illumination
of the recording beam instead of increasing the sensitivity. This is
accomplished by moving the mechanical slit and associated condenser
closer to the galvanometer. If the sensitivity of the modulator is
kept constant, the illumination at the film is directly proportional to
the square of the number of sloping edges and inversely proportional
to the square of the slope.

268

G. L. DlMMICK

[J. S. M. P. E.

Fig. 12 shows three types of variable- width sound-track together
with the form of aperture required for each. They are (a) the standard
bilateral track, (b} the class B push-pull track, and (c) the class A push-

FIG.
curve)

10. Effect of bias condenser upon galvanometer impedance : (broken
no bias condenser; (solid curve) 0.035 rf across biasing winding.

pull track. Many other types such as the unilateral and multilateral
tracks are easily obtained. The black rectangles represent the
shutter vanes that mask the unused portion of the light-beam for
noise-reduction. The class B track requires no noise-reduction,
but inherently possesses a higher signal-to-noise ratio than any other

Slit

'Lijhl

FIG. 11. Two methods of making variable- width sound records.

known system of film recording. At the present time, the class B
track is not suitable for general theater release, because of the neces-
sity of maintaining an accurate sensitivity -balance in the push-pull
reproducer. The class A push-pull track does not require that the

Sept., 1937]

RCA RECORDING SYSTEM

269

reproducer be accurately balanced, and the recording is no more diffi-
cult to handle than for standard track. In converting a recording
optical system from standard to class A push-pull, it is necessary
only to change apertures, the same shutter being used in both cases.
If it is desired, however, the speed of the shutter operation may be
increased, since modulation of the light-beam by the two vanes is in
phase and is largely cancelled in the push-pull transformer. High
frequencies reproduced from the variable-width push-pull class A

(b)

(c)

FIG. 12.

Three types of variable-width sound-track: (a) Standard bi-
lateral; (b) Class B push-pull; (c) Class A push-pull.

track are exceptionally clean even though the print and negative
densities vary somewhat from the values recommended for standard
track. This is true because even-harmonic distortion and distortion
due to audible variations in average transmission are not reproduced.
Variable-Density Recording. — The advantages of the light-modu-
lator are by no means limited to variable-width recording. Linear
variable-intensity modulation of a quarter-mil light-beam may be had
without reducing the optical efficiency or sacrificing the advantage of
visual monitoring. The method of converting from angular-mirror
vibrations to light-intensity variations is shown in Fig. 13. A rec-
tangular beam of light is focused upon the slit in such a manner that

270

G. L. DlMMICK

[J. S. M. P. E.

three of its edges are sharply defined, while the fourth edge (parallel
to the slit) is given a linear gradation in intensity.4 The beam is
vibrated at right angles to the slit, causing the transmitted light to
vary with the position of the rectangle. Fig. 14 shows how a linear

gradation or penumbra may be
formed. Light from a source F, of
uniform brightness, is observed
from the three positions A, B, and
C. The straight edge of an opaque
aperture £ is on a line between the
center of the source and point B.
It is evident that from point A
none of the filament can be seen,
from point B half the filament is
visible, and from C all of it is
visible. The gradation of light in-
tensity from A to C is therefore
linear.

Fig. 15 shows how this principle
is applied to the recording optical
system. The only changes in the optical layout are the addition of
the penumbra aperture T and the cylindrical lens N, and the elimina-
tion of the ultraviolet filter /. The aperture C is rectangular in shape
and is focused upon the slit as before. Part of the light passing one
of its edges is intercepted by the aperture T, forming a penumbra at

FIG. 13. Penumbra light-beam
and slit for standard variable-density
recording.

_ --A
8

FIG. 14. Formation of linear penumbra.

the slit like that shown in Fig. 13. It makes no difference in the
final result whether the penumbra aperture is placed between the
lamp and rectangular aperture or between the rectangular aperture
and the intermediate lens. It is of practical importance, however,
to place it inside the closed condenser barrel where it may be kept
clean. The purpose of the cylindrical lens N is to produce a slight

Sept., 1937]

RCA RECORDING SYSTEM

271

magnification of the filament image in a vertical plane and allow this
image more than completely to fill the galvanometer mirror. In

FIG. 15. Modified optical system for standard variable-density recording.

this way any irregularities of the upper and lower edges of the filament
coil are cut off and do not effect the linearity of the light gradation
at the slit. The height of the penumbra is determined by the height

FIG. 16.

(b)

(a) Penumbra masks for class A push-pull variable-density re-
cording; (b) apposed penumbras at the slit.

of the mirror and the distance between the two apertures T and C.
This height is so adjusted as to require approximately the same gal-
vanometer deflection for 100 per cent modulation of both variable-
width and variable-density tracks.

272

G. L. DlMMICK

[J. S. M. P. E.

Ground-noise reduction for the standard variable-density track
is accomplished by biasing the galvanometer. The noise-reduction
amplifier used to operate the variable-width shutter system performs
equally well for variable-density. When there is no modulation,
the penumbra is shifted so that the slit is nearest the dark side.

Class A push-pull variable-density tracks are also possible with
very little change in the optical system. Fig. 16 shows the required
penumbra aperture and the appearance of the light-beam at the slit.
The two adjacent penumbras face in opposite directions so that as
the whole light-beam is vibrated across the slit the quantity of light

FIG. 17. Modified optical system for push-pull variable-density recording.

passing through one half is increasing while that passing through the
other half is decreasing.

The layout of the optical system for class A push-pull variable-
density is shown in Fig. 17. Cylindrical lens V is used in combination
with the intermediate spherical lens E. In the vertical plane the
spherical lens forms an image of the rectangular aperture C upon the
slit. In the horizontal plane the combination of the cylindrical and
spherical lenses forms an image of the penumbra masks upon the
slit. The cylindrical lens next to the lamp is not required here as it
was for the standard variable-density system. The cylindrical lens
V tends to shorten the length of the filament image. When this is
overcome by increasing the magnification of condenser B, the height
of the image more than fills the mirror, as desired.

Noise-reduction may be effected by making the two penumbra
masks the vanes of a double-vane shutter similar to the shutter em-

Sept., 1937] RCA RECORDING SYSTEM 273

ployed for standard and push-pull variable-width recording. When
the modulation is low the current operating the shutter increases,
pulling the penumbra masks apart and shifting the penumbras in op-
posite directions so that the illumination of both halves of the track
is reduced.

Acknowledgment of important work that has contributed to the
development of the above-described light-modulating system is due
Messrs. A. C. Hardy, E. W. Kellogg, C. R. Hanna, L. T. Sachtleben,
H. J. Hasbrouck, J. O. Baker, and C. N. Batsel.

REFERENCES

1 MACKENZIE, D.: "Sound Recording with the Light-Valve," /. Soc. Mot.
Pict. Eng., XH (Sept., 1928), No. 35, p. 730.

2 HARDY, A. C. : "The Optics of Sound Recording Systems," J. Soc. Mot. Pict.
Eng., XII (Sept., 1928), No. 35, p. 760.

3 DIMMICK, G. L. : "Galvanometers for Variable-Area Recording," /. Soc.
Mot. Pict. Eng., XV (Oct., 1930), No. 4, p. 428.

4 SACHTLEBEN, L. T. : "Characteristics of Photophone Light-Modulating
System," /. Soc. Mot. Pict. Eng., XXV (Aug., 1935), No. 2, p. 175.

DISCUSSION

MR. SKINNER: Push-pull recording seems to have the advantage of cancelling
the ground-noise, yet in all cases you have two different systems and still add
shutters to reduce the noise. Is it possible, theoretically, to cancel the noise
without shutters?

MR. DIMMICK: The Class A push-pull method does not reduce ground-noise
any more than the standard types of tracks. The standard push-pull B does,
by virtue of the fact there is no modulation and the track is almost completely
black. In the Class A push-pull system it is necessary, as well as with the stand-
ard tracks, to use the shutter system for noise-reduction, but the push-pull
arrangement considerably improves the response at high frequencies, eliminates
the distortion that might otherwise exist at those frequencies, and eliminates
any shutter noise that may occur due to the movement of the shutter lens.

MR. SKINNER: It seems to me that there is some sort of cancellation, at least
of ground-noise.

MR. DIMMICK: As far as I know the variations produced by the ground-noise
are not cancelled in a push-pull transformer, since they are random variations.

A DEVICE FOR DIRECT REPRODUCTION FROM VARIABLE-
DENSITY SOUND NEGATIVES*

W. J. ALBERSHEIM**

Summary.— The possibility of reproducing sound directly from the negative record
offers an improvement in sound quality because it avoids the deterioration of defini-
tion, wave-shape, and volume range caused by the printing process.

In order to eliminate the distortion inherent in variable-density sound negatives,
the playback amplifier must produce the same type of compensating distortion that
occurs in good straight-line prints. The theoretical circuit requirements for an
amplifier of this type are derived, and the RA-222 negative playback amplifier de-
veloped by the ERPI engineering department, in accordance -with these requirements, is
described. In addition to the basic distortion circuit, the RA-222 amplifier satis-
fies practical requirements, such as self-contained power supply and adjustments
for negative gamma, amplitude, and frequency characteristic.

Experiences in various fields of use are reported, such as sensitometric measure-
ments, print control, re-recording, and high-quality reproduction.

In the production of sound recordings on film, two photographic
steps are involved. First, one obtains a negative sound record by
direct exposure to light modulated by the sound signals. In the sec-
ond step, a positive record is obtained by a printing process. It is
inevitable that the second photographic step introduces quality losses.
These losses are of a double nature : the sharpness of the signal image
is diffused, and thereby high-frequency losses and distortions are
introduced; and the graininess of the positive emulsion increases the
background noise level. A better sound quality can therefore be
expected if it is possible to eliminate the printing operation.

Successful attempts have been made to obtain negatives that can
be reproduced directly. In variable-density recording these are
known as "toe" negatives. Anybody who has heard reproduction
of good toe negatives admits the great clarity and firmness of tone

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
19, 1937.

** Electrical Research Products, Inc., New York, N. Y,

274

REPRODUCTION FROM SOUND NEGATIVES 275

shown by these films. Toe records, however, are subject to several
limitations. They can not be commercially produced in sufficient
quantity for theater release. Furthermore, the curvature of the
toe characteristic introduces harmonic distortion unless the modula-
tion is held fairly low, and thus their noise level is as high as or higher
than that of prints.

In some special fields, such as in editing newsreels, so-called
straight-line negatives have been reproduced without printing. The
sound from these negatives is, of course, badly distorted by the curva-
ture of the negative characteristic, but listeners were invariably im-
pressed by the low noise-levels of these negatives, which is due to the
finer grain of films developed to a low gamma.

Based upon these advantages of sound negatives, the Engineering
Department of Electrical Research Products, Inc., set itself the task
of providing electrical means by which a straight-line negative could
be reproduced free from distortion. These electrical means must
produce a compensating amplitude distortion equivalent to that which
occurs in an ideal photographic printing process. Since the planned
device must be capable of reproducing negatives that were de-
veloped to different degrees of contrast, it must contain a control
that permits an adjustment of the "apparatus gamma." The gamma
adjustment had to be independent of the signal frequency, and could
therefore contain only resistive elements, such as a rheostat or gain
control. This requirement practically determined the design of the
entire device, as will be shown by the following mathematical reason-
ing:

If 6i is the instantaneous input voltage and e0 the output voltage,
the analogy of a straight-line printing process requires that

e0 = Cei-r (1)

Now, at the gamma control point the signal voltage ec is an un-
known function of the input voltage and of the output voltage

ee=f(ei-r) (2)

The control feature requires that an amplitude change of ec pro-
duces a gamma change in the over-all characteristic; therefore

»/(*-') =/(*-*r) (3)

The only function that satisfies equation 3 is the logarithm. It
is therefore necessary that the voltage change at the control point be
proportional to the logarithm of the output. Incidentally, due to

276 W. J. ALBERSHEIM [J. S. M. P. E.

equation 1, it is also proportional to the logarithm of the input volt-
age, as expressed by equation 4;

ec = k log e0 = — kr log 0, (4)

In order to transform this logarithmically distorted signal into the
desired linear characteristic, it has to be subjected to an exponential
amplitude distortion as shown in equation 5;

(5)

This type of distortion is easy to achieve, because amplifying tubes
with exponential characteristics were developed years ago for the
purpose of volume control. There remains the task of providing a
logarithmic volume distortion for the "volume control stage." No
tubes with logarithmic characteristics are available. However, if
one impresses a linear characteristic upon the anode of an exponential
tube, then its control grid will perforce follow the inverse function of
the exponential tube characteristic, which is the desired logarithmic
function. In the device here described the linear response of the
plate was obtained by reverse feedback. Fig. 1 shows schematically
the circuit diagram of the RA-222 negative playback amplifier de-
veloped by the Engineering Department. The first tube shown at
the left is a high-mu, straight-line amplifier tube. Its output volt-
age is coupled to the grid of the second tube, which is an exponential
type of amplifying tube, and the space-current of the second tube is
fed back into the grid circuit of the first tube. Thus, over a wide
range of input voltage the grid-swing of the second tube is propor-
tional to the logarithm of the input voltage. This reverse feedback
has the additional desirable effect of stabilizing the input tube and of
reducing its internal distortion as well as its effective input imped-
ance. Thus it becomes possible to connect the attachment to the
photocell terminals of existing apparatus through a low-capacity
cable of reasonable length without undue loss at high frequencies.
This is doubly important because the input voltage is proportional
to the distorted transmission of a straight-line negative. If its
harmonics are suppressedi they appear as inverted harmonics in the
output of the negative playback amplifier.

It is difficult to utilize the logarithmic grid voltage of the second
tube directly for control purposes because if power is drawn from this
high-impedance circuit the logarithmic amplitude is distorted. This
logarithmic grid voltage is, therefore, impressed directly upon the
grid of an auxiliary straight-line amplifier tube, tube No. 3. This

Sept., 1937] REPRODUCTION FROM SOUND NEGATIVES

277

tube serves a double purpose. It isolates the control circuit from
the logarithmic feedback circuit, and provides gain and power for
control purposes. In addition, it reverses the polarity of the loga-
rithmic signal as required by equation 4. That such a reversal is
necessary becomes evident from the consideration that in the photo-
graphic printing process, as well, the optical transmission of the record
changes inversely as the illumination.

The output voltage of the third tube is adjusted in amplitude by the
gamma control, shown in the schematic diagram as RU, and impressed
upon the grid of the exponential output tube TV

This completes the list of basic circuit elements. Actually there

FIG. 1. Schematic diagram of playback amplifier.

are, of course, a number of additional practical requirements: The
amplifier must be capable of reproducing not only the signal fre-
quencies but also the d-c. components caused by even harmonics and
by noise-reduction bias. Therefore, the entire structure from the
grid of the input tube to the anode of the output tube is a straight
d-c. amplifier containing only resistive elements. In view of the
high gain in the first stage it is necessary to compensate for the varia-
tions in the space-current of individual tubes by providing the rheo-
stat Ri6. A similar precaution is taken in the screen-grid circuit of the
third tube by providing a potentiometer PI. Finally, the initial
value of the gamma control Rn is connected to an auxiliary rheostat
RIZ in order to fit the calibration of the gamma control to the exponen-
tial gain characteristic of the output tubes.

Further problems were introduced by the fact that the exponential

278 W. J. ALBERSHEIM [J. S. M. p. E.

tubes contain not only exponentially acting control grids but also
screen-grids of a more nearly linear characteristic; and finally, the
entire unit was to be operated from a single power-supply which in-
troduced an inter-coupling of all the tube elements through the various
bleeder resistances. It was found necessary to introduce compensat-
ing or "neutralizing" resistance connections at various points in order
to offset amplitude distortions that might otherwise have been caused
by this inter-coupling.

The remainder of the circuit elements are of an auxiliary nature
for convenience of operation. An output transformer was connected
to the plate circuit of the output tube in order to match the normal
500-ohm or 200-ohm system amplifier inputs. At this point a trans-
former is permissible because the harmonic distortions have been
eliminated and the d-c. components are no longer essential. The
output circuit is also equipped with a low-frequency equalizer and an
attenuator in order to transmit to the system amplifiers a level and a
frequency characteristic similar to those of a normal photoelectric
cell amplifier. In addition, the equipment provides a switching ar-
rangement that makes it possible to change over from negative play-
back to a straight photoelectric cell amplifier circuit for print repro-
duction. This is accomplished by connecting the linear space-cur-
rent of the second tube into the output circuit.

A group of push-button keys makes it possible to measure the plate
currents of all the tubes on a single milliammeter MI.

The locations of the various controls are visible in Fig. 2, which is
a photograph of the assembled negative playback amplifier with its
power unit.

In tuning up, the operator first allows the apparatus to warm up
for a few minutes. Next, the coupling resistor R16 is adjusted for
the correct plate current of the second tube. Third, a direct current
of 0.15 milliampere is impressed upon the anode input. This can be
done by connecting the positive terminal of a 1.5- volt dry cell to
ground and the negative terminal through a series resistance of 9
megohms to the anode terminal. With this input, Pt is adjusted
until the plate current of the fourth tube equals about 1 milliampere
regardless of the gamma control setting. Finally, the gamma con-
trol is adapted to a negative gamma of 0.5, and the gamma vernier
R,2 is adjusted until the apparatus gamma equals two divided by the
ratio of specular to diffuse gamma, that is, about 1.5.

The apparatus gamma can be measured either with direct current,

Sept., 1937] REPRODUCTION FROM SOUND NEGATIVES

279

by plotting input versus output currents on a log scale, or with a com-
bination of direct and superimposed alternating current by noting
the output attenuation that compensates for a given input attenua-
tion. Once these adjustments are made, they remain unchanged
until one of the tubes becomes exhausted and has to be exchanged;
that is, for several months at a time.

FIG. 2.

Negative playback amplifier with
power unit.

The apparatus here described has been tried out over a considerable
period of time, and the following uses have been made of it :

(2) Newsreel records were judged and edited from negatives.

(2) Sensitometric measurements were made by finding minimum distortion
of single-frequency test-films and " Adb." tester.

(3) Prints of unsatisfactory quality were checked by comparing them with
the quality of the original negative. In some cases it could be shown that the
negative had been developed to an unusual gamma by observing the setting of
the gamma control at which the best sound quality was obtained from the nega-
tive.

(4) Feature films were re-recorded directly from the original negative, thus
avoiding the quality losses in the printing process.

280 W. J. ALBERSHEIM

(5) For special showings the negatives were played in synchronism with posi-
tive pictures by means of a double-film reproducing attachment.

Experience has shown that the equipment is especially suited for
the reproduction of noise-reduction negatives. The "hush-hush" is
greatly reduced because the unbiased noise-level is lower. Never-
theless, the effective amount of noise-reduction is greater in the nega-
tive than in the print, because in the print, low-level signals corre-
spond to darkened film having decreased volume range; whereas in
the negative, low-level passages increase the transmission and the
volume range of the film.

Since the negative playback amplifier produces reciprocal amplitude
distortion, a decrease in lamp current increases the output signal, and
vice versa. For this reason, clear film should be used as leader when
reproducing negatives, and splices should be punched out just as
they are in preparation for the printing process.

AN AUTOMATIC SOUND-TRACK EDITING MACHINE*

G. M. BEST**

Summary. — The sound-track cutter requires a film reproducer in his daily routine
work: a reproducer that can be threaded quickly and will not tear or damage the film,
and will produce sound quality of sufficient excellence to judge splits or cut-outs in
music recording.

Such a device has recently been developed, and its mechanical details and operation
are described. By means of a geared motor drive and a series of friction rollers, the
sound-track is fed past the light-beam of the reproducing system at standard speed,
with a reversible feature that is automatic and instantaneous. No sprockets or clamp
rollers are used, and the work of the cutter is speeded materially through its use.

In most studios the dubbing room staff includes a number of sound-
track cutters and assistants who prepare the speech, music, and sound
effects for the dubbing mixers. Each cutter is provided with a room
equipped with the conventional moviola and track units, which can
be coupled together or run separately, as desired.

In assembling the various tracks, frequent use of the track repro-
ducer alone is required, and when a number of tracks are to be assem-
bled in a hurry, the operation is slowed down by the necessity of
threading the film through the reproducer, which may not always be
in a convenient position on the cutting table. In addition, the ma-
chine must be started, stopped, and reversed with hand switches,
and a wrong move frequently results in torn film, requiring reprints
and consequent delays. Most reproducers for cutting purposes are
equipped with a non-synchronous motor, the speed of which is not
constant over a period of time. In editing music tracks this has
proved a handicap, as it is not easy to judge accurately the timing
of music with a reproducer that is running faster or slower than the
correct tempo.

Sprocketless reproducers for quickly checking sound- tracks have been
made available upon the market, but the film movement is by hand-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
21, 1937.

** Warner Brothers Pictures, Inc., Burbank Calif.

281

282

G. M. BEST

[J. S. M. P. E.

power through the rewinds, and the suitability of such a device for
reproducing music is questionable. To eliminate these objections,
and provide a film reproducer that would run at a constant speed of
90 feet per minute, without sprockets, clamp rollers, or other poten-
tial film hazards, Major Nathan Levinson, Director of Sound at Warner
Bros. Studios, suggested a device that has been worked out and placed
in operation with gratifying results.

The reproducer, a front view of which is shown in Fig. 1, consists
essentially of a synchronous 110- volt motor geared to two polished
steel rollers in such a manner that the peripheral speed of either roller

FIG. 1 (a). Front view of editing machine.

is 90 feet per minute. Between the two rollers is mounted an optical
system, with exciting lamp and photoelectric cell, with a pair of aper-
ture plates spaced so as to line up the film accurately with the optical
system without scratching the film. In each plate, an aperture ap-
proximately 0.09 inch square is cut, to pass the light-beam and mask
the track in a manner similar to standard theater sound reproducing
practice. The driving rollers are flanged at both ends to keep the
film in line, and an additional guide-roller, although not absolutely
necessary, is placed outside the right-hand driving roller to aid in
steadying the film.

Fig. 2 is a side view of the device, section A showing the details of
the aperture plate and photoelectric cell, and section B the relation
of the driving motor and gears to the driving rollers. Above each

Sept., 1937]

SOUND-TRACK EDITING MACHINE

283

driving roller, and hinged to the frame in which the gears are housed,
is an idler roller, recessed to avoid scratching the sound-track, and

Fig. 1 (6). Upper front view of editing machine.

held out of the way by springs when not in use. These rollers may
be clamped down upon the driving rollers by gentle pressure of the
hand; when neither roller is depressed, the film stands idle in the

FIG. 2. Side view of reproducer: (A) details of aperture plate and photo-
electric cell ; (B) arrangement of driving motor, gears, and rollers.

aperture, the weight of the film on top of the driving rollers being in-
sufficient to propel it one way or the other.

If the film is to be reproduced normally, the left-hand idler roller
is clamped down upon the film, and the device operates in the manner

284 G. M. BEST [J. S. M. P. E.

of a clothes wringer, bringing the film instantly to standard speed and
direction. If the film is to be run backward, the right-hand idler
roller is depressed, and the film is drawn past the aperture in back
motion. Thus a section of film only a few frames in length can be
drawn back and forth, and a single word or music phrase can be played
again and again, until the cutter determines the exact point where
he wishes to make a cut or split, whereupon he marks the film. If
sections of film several hundred feet apart are to be checked in one
reel, the motor can be cut off, and the film drawn through by hand
until the next section to be checked is reached, using the set-up shown
in Fig. 3.

This arrangement is one designed for locating the correct position

FIG. 3. Film-editing machine installation.

for printer-light changes in variable-density release printing. In
routine checking of the finished job turned out by the dubbing room,
it is customary to run the separate picture and sound-track in the
projection room, and to make notes of volume changes required to
increase the volume range of the effects or music, and to take care of
inaccuracies in the leveling of dialog by the dubbing mixer. These
volume changes are obtained by the well known method of lightening
or darkening the track during the printing operation, and the labora-
tory requires accurate data regarding the location of each notch in
the sound-track negative where the printer light is to be changed.
Using the notes obtained in the projection room, the track and pic-
ture prints are set up as shown in the photograph, with the automatic
editing machine set between the footage counter and the right-hand

Sept., 1937] SOUND-TRACK EDITING MACHINE 285

rewind, and lined up so that the sound-track passes in a straight line
from the left rewind through the counter and editing machine to the
opposite rewind. The film can then be run through either by hand
or motor power until the spots where volume changes are to take
place have been located, and the section run back and forth until the
exact spot for the notch is determined. The distance relative to the
start mark is then noted upon a report, and the laboratory notches
the corresponding negative at that spot.

The output of the selenium photoelectric cell in the editing repro-
ducer is connected to a three-stage amplifier similar to that used in
all cutting room installations, and the sound is reproduced from a
loud speaker set in a convenient place on the cutting table. Ad-
mittedly, the film movement of the machine is not perfect, and a cer-
tain amount of gear noise is heard in the loud speaker, but it does not
interfere with either the intelligibility of speech or with the music re-
production, and as the flutter is in synchronism with the motor and
gear noise heard directly, the ear tends to discount the interference.

A DUBBING REHEARSAL CHANNEL*

H. G. TASKER**

Summary. — Preparation of sound effects, music, and dialog tracks for dubbing
requires accurate synchronization of each sound with the corresponding action. This
is ordinarily accomplished by a preliminary step in which the synchronism of one
sound-track at a time is checked against the action in a moviola, in which the picture
is seen through a small viewing lens.

The image being small, the accuracy with which synchronism may be checked is
not good. Hence this is followed by a final step, in which the synchronism of all tracks
is checked during rehearsals in the dubbing-room proper. Owing to the ponderous
character of the dubbing machinery the latter process is quite slow and laborious.
This paper describes the form and use of a machine that permits accurate synchronism
of the various sound-tracks with the corresponding action, but with all the mechanical
freedom of the usual moviola.

The machine will accommodate six sound-tracks, with provision for controlling the
output level from each, and may be instantly started, stopped, or reversed. The
mechanical design facilitates threading and easy displacement of any sound-track by
a known amount to bring it into synchronism. The action is projected upon a
screen 4l/2 X 4 feet in size, which enables accurate observation of the degree of syn-
chronism attained.

An important gap has existed in the studio facilities for handling a
picture in the stage between the editing and the dubbing processes.
In the typical method of handling this intermediate stage, which we
may describe as "dubbing preparation," a staff of cutters, deriving
their general instructions from the music, editorial, and sound de-
partments and from the director or producer, "build" the sound-
tracks to provide supplementary effects and music required for a
complete dramatic presentation of each reel of the picture. These
cutters first review the picture in the projection room, making note
of the comments of the director and producer and adding their own
general notes, after which they obtain the necessary sound-tracks
either from the library or from new recordings for this picture. In
the course of getting the material together each cutter privately re-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
22, 1937.

** Universal Studios, Universal City, Calif.

286

DUBBING REHEARSAL CHANNEL 287

views each reel several times to make sure that he is getting the right
material.

The work of assembling the sound-tracks into reels, accurately
spacing them so that they will synchronize perfectly with the action,
is usually done on sound moviolas, wherein the picture is viewed
through a small viewing lens. The apparent size of the image is less
than 2X3 inches, hence very close inspection is required to determine
whether any given sound effect or musical beat is in synchronism
with the action. Moreover such moviolas are usually provided with
one (or not more than two) reproducing sound unit and hence the
sound effects and music tracks must normally be checked one at a
time. This is no handicap except where certain overlapping sounds
are interrelated, but it often happens that this interrelation is just
as important as the relation of either to the action — for example, in
the case of dance taps.

Not only do errors creep in from such causes which must ultimately
be discovered by viewing the picture and hearing the sound under
more nearly theater conditions, but it is also common practice that
the director, producer, musical director, and chief sound-effects cutter
shall have an opportunity to review the whole effort under such con-
ditions in order to pass judgment upon the merit of the material se-
lected as well as to check the accuracy of its placement.

It has been customary at several studios for this checking to be
done on the dubbing channel itself. Aside from the fact that it ties
up a good deal of dubbing channel and dubbing crew time, this would
seem at first glance to be an ideal arrangement. However, a certain
difficulty arises because of the ponderous nature of the dubbing chan-
nel machinery, together with the fact that the sound accompaniment
for many reels is very complex and requires careful and detailed re-
view. When making this critical review of a reel it would be very
desirable if we could run down through the first three or four points
requiring comment or discussion, then stop to make adequate notes
or decisions upon the points, then to continue through the next small
portion of the reel, etc. Sometimes, in fact frequently, it is highly
desirable to repeat a section several times until there is complete
agreement as to the desirability of proposed changes. However,
present-day dubbing machinery is not reversible, and the time re-
quired to stop it, rewind, and re-thread five to eight sound-tracks
and start again is prohibitive. For this reason it has been current
practice to run the entire reel, making note of three or four most im-

288

H. G. TASKER

[J. S. M. P. E.

portant points, then re-run it to confirm these points and pick up two
or three others, after which it is sent to the cutting rooms for the nec-
essary changes. However, it is a rather difficult matter to carry ac-
curately in mind a large number of brief impressions, and the job of
inspection just described becomes very superficial, particularly in the
case of complex reels, so that it almost invariably happens that upon
completion of the changes mentioned above (which may take a mat-
ter of hours to identify and complete) there will still be found a num-
ber of less important changes to make. Moreover it was not uncom-

FIG. 1. View of the sound mechanism, showing method of threading.

mon to find that the original decision for a change was made upon
such superficial examination that the change proved undesirable and
the original condition had to be restored.

A great simplification of this problem, together with a substantial
saving in time and improvement in accuracy can be accomplished by
means of the dubbing rehearsal channel described in the following
paragraphs. The heart of this channel is a combined action and
sound reproducing machine capable of reproducing as many as six
sound-tracks simultaneously, and which projects a picture 3 feet by
4 feet in size, and yet has all the features of flexibility that distinguish
the usual moviola. The machine runs as well in reverse as it does

Sept., 1937]

DUBBING REHEARSAL CHANNEL

289

forward, reverses almost instantaneously, starts and stops readily,
is very easily threaded, has provision for individual volume control
of the several tracks, and produces quite satisfactory picture bright-
ness and sound-quality.

Fig. 1 is a general view of the sound-reproducing part of the mech-

FIG. 2. View showing relation of sound and action units to
motor drive.

anism. Note that the six sound-sprockets are mounted on a single
sturdy shaft approximately 1 inch in diameter with three-bearing
support. A second main shaft drives 12 take-up spindles through
as many belts. Threading is reduced to the simplest possible terms.
Only the little pressure roller at the scanning point needs to be re-
leased during threading, as the other four rollers are in fixed positions
and are so shaped that the film may be slipped between them with

290

H. G. TASKER

[J. S. M. P. E.

the simplest of motions. In spite of the fact that the six feed-reels,
the six sound-sprockets, and the six take-up reels are respectively
coaxial, the machine has been so designed that no obstructions are
encountered in threading and the film may be placed upon or removed
from the machine as easily when half the length of the film is on either
reel as when one reel is empty.

The little rectangular box in front of each sound-sprocket contains
the exciter lamp, sound optic, and photocell. As seen in Fig. 2 the
latter receives its light from a small concave mirror located immedi-

FIG. 3.' Sound reproducer unit, showing optical path.

ately behind the film, since the large sound-shaft prevents placing the
cell itself behind the film as in conventional reproducers. The sound-
sprockets are not keyed to the sound-shaft but are driven through
retractable pins in the associated collars, which latter are keyed to the
sound-shaft. Each of the 32-tooth sound-sprockets has eight holes
to receive the retractable pin. Consequently, any one of the several
sound-tracks may be advanced or retarded in one-frame intervals
provided the machine is at rest.

Fig. 3 shows the sound mechanism in its relation to the motor
drive and the picture projector. The picture projector is a Simplex
head in which the gate has been modified to permit reversal of the
mechanism without buckling the film, and is driven from the slow-

Sept., 1937]

DUBBING REHEARSAL CHANNEL

291

speed, three-phase synchronous motor through a crude but sufficiently
effective elastic drive visible on the flywheel end. The need for this
elastic coupling arises from the following considerations :

Design of the sound mechanism is such that the synchronous motor
is relied upon for constancy of speed, the two shafts of the sound re-
producer being driven from the synchronous motor through a pair of
precision gears. Maximum constancy of motor speed is attained by

FIG. 4. Diagram of cell and mixer circuit.

selecting a motor of several times the required power so that it will
lock accurately to the line frequency and be nearly independent of
variations in take-up loads, etc. Such a motor, even though provided
with moderate starting resistances and fairly substantial flywheel,
will accelerate the system much too rapidly for the Simplex projector,
particularly because of the considerable inertia of the flywheel on the
Simplex intermittent.

Furthermore, the semi-instantaneous reversal of the system, which
is so very desirable, still further aggravates the abuse to which the
projector would be submitted were it not elastically coupled to the

292 H. G. TASKER

motor. The present combination of elastic coupling with resistors of
low value connected in each leg of the three-phase motor make it
possible to start, stop, and reverse the system with complete freedom.

The transmission system of this machine is quite simple. A single
amplifier of an inexpensive type provides all the amplification re-
quired plus field supply for the loud speaker. Although individual
volume control is provided for each channel there are no associ-
ated individual amplifiers. Instead, the gain control is secured by
varying the anode voltage of the photocells, as shown in Fig. 4.
Small signal leakage which persists at zero anode voltage may be
eliminated by throwing the key associated with each cell which ap-
plies a small negative potential to the anode. All six of the cells are
connected through a common circuit to the first tube of the amplifier.
Exciter lamp supply is raw alternating current, and the fundamental
hum frequency (100 cycles, since Universal Studio is equipped with
50-cycle supply) is reduced approximately 20 db. by a very sharply
resonant equalizer. The hum will be still further diminished when
this machine, like our moviolas, is equipped for push-pull.

A 500-watt projection lamp and watercell filter seen at the right of
Fig. 4 supply the needed illumination for projection without danger of
burning the film even when the projector comes to rest during re-
versal. The usual fire shutter further diminishes the fire hazard.

It is particularly helpful, when a timing error has been discovered
by use of this machine, to be able to determine definitely which track
is in error and by how much. By means of the keys provided in each
of the mixer circuits all but one of the sound-tracks may be turned off
and the remaining one checked accurately with the picture. If found
to be satisfactory the next track is tried, and so on, and when the
faulty track has been discovered it is put into synchronism with the
action by the frame-shifting feature mentioned above, and the amount
of shift is logged in the cutter's notes. Since errors of this sort usually
occur in relatively short passages, it is readily seen how valuable the
reversing feature of the machine may become. A fifteen-second pas-
sage may be checked, reversed, checked again, reversed, and checked
a third time in one minute and twenty seconds, and a synchronism
change can be made and checked in one additional minute.

The sound- quality, while not exceptional, is quite satisfactory for
the purpose, and is limited more by the use of the ordinary type of
dynamic loud speaker than by any other feature. The flutter, while
readily noticed, is low enough so that it does not interfere appreciably.

THE EVOLUTION OF SPECIAL-EFFECTS
CINEMATOGRAPHY FROM AN ENGINEERING VIEWPOINT*

F. W. JACKMAN**

Summary.— Special-effects cinematography furnishes a means of filming scenes
that can not be filmed easily, safely, or economically by conventional methods. Various
kinds of special-effects camera work are described, including multiple exposure,
multiple printing, travelling-matte systems of printing and photography, the pro-
jection background process, optical printing, and miniatures. The fundamentals
of the processes are outlined, and the relations of the special-effects department to the
studio organisation are discussed.

The strictly technical details of the various special-effects processes
have been fully covered in papers published from time to time in the
JOURNAL. This paper will therefore seek to describe another and
equally important phase of special-effects cinematography; namely,
the relation of the work to the practical routines of commercial pro-
duction.

In doing so it is necessary to review the development of this kind
of work, especially in order to emphasize the tremendous difference
between the magic-working trick cameraman of a few years ago and
the special-effects engineer of today. The former was merely an in-
genious craftsman ; his present-day successor is more nearly compar-
able to a production executive than to anything else. In addition to
being a technician and artist of high attainments, he must be a
capable executive who can first sell to his studio the merits of special-
effects work, and then organize and operate a department that is
truly a studio within a studio. He must do so on an unfailing com-
mercial basis, thus proving that he is saving his studio money every
time he makes a special-effects shot.

Special-effects cinematography has but one excuse for existing:
it makes it possible to put upon the screen scenes that would by
ordinary methods be either impossible or too difficult, dangerous, or
expensive to produce commercially.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
21, 1937.

** Fred Jackman Process Corp., Burbank, Calif.

293

F. W. JACKMAN [J. s. M. p. E.

As an example of this, the part played by special-effects camera-
work in filming an important feature made about a year ago at a
major studio may be cited. The story of the picture involved several
seventeenth century frigates and galleons. At least two ships had
to be used; three would have been dramatically preferable. The
greater part of the story hinged upon them and upon the bombard-
ments, sea battles, etc., in which they participated.

To construct full-sized ships and employ straightforward camera
methods would have meant an outlay running well into six figures.
Manning the fleet, providing the necessary camera ships, tugs,
launches, and the like, and operating them at sea for the weeks or
even months necessary to wait for the proper weather would have
increased the cost of making these scenes to a sum far exceeding any
budget practicable for filming the entire production. In addition,
another sequence, in which a frigate shells and destroys an attacking
flotilla of rowboats, would have been virtually impossible to film
safely by ordinary means, for as the rowboats were destroyed, the
men in them would have been thrown into the water, and an explosion
capable of sinking a rowboat would have been transmitted by the
water with force sufficient to injure and perhaps kill any men in the
water within a hundred-foot radius.

The scenes were therefore done by means of miniatures. Three
miniature ships were constructed for slightly more than a thousand
dollars apiece, and served quite as well as full-scale ships. Every
bit of special-effects photography in the picture, including not only
the ships and all the other miniatures, but also the routine special
effects such as projected-background process shots, fades, dissolves,
wipes, and the like, were delivered for less than half the cost of one
full-scale ship. In other words, the difficult, dangerous, and prohibi-
tively expensive scenes were filmed in perfect safety for approxi-
mately one-quarter of the cost of merely constructing — not using —
two full-scale ships.

Time was saved as well as money. Done by ordinary methods,
the sequence in which the rowboats were destroyed would have re-
quired from four days to a full week of strenuous and expensive work
with a full company. The miniature was filmed in half a day. The
battle sequences, without allowing for the inevitable delays due to
unfavorable weather, could not have been filmed conventionally in
less than three weeks. The location of the -studio tank made it im-
possible to shoot before 1 1 : 30 in the morning or after 2 : 30 in the after-

Sept., 1937] SPECIAL-EFFECTS CINEMATOGRAPHY 295

noon; but even so, the whole sequence was filmed in four 4-hour days.

Most important of all, the head of the special-effects department
was able to plan both the technical and the economic aspects of the
job with such accuracy that he was able to lay before the production
executives an estimate guaranteeing the desired effects at a guaran-
teed cost and within a guaranteed time. The scenes as they were
actually used gave precisely the effect intended. They were achieved
at a cost slightly below the original estimate, and delivered ahead
of schedule.

This case, while perhaps more spectacular than usual, is a typical
example of the technical and economic precision of modern special-
effects work. The modern special-effects engineer performs his work
on the basis of thoroughly known principles, and he is able in ad-
vance to predict both the result itself and the cost of obtaining it.

In the earlier days of the industry, the few cinematographers who
practiced what was then called "trick camera work" were regarded
almost as so many magicians. They did not always know how suc-
cessfully their magic was going to turn out, but they tried, and learned
— and in learning laid the foundation of today's knowledge and prac-
tice.

One of the earliest principles they discovered was that of multiple
exposure, followed by multiple printing. By keeping the camera
motionless and making, say, two exposures with alternate halves of
the frame matted out, a good number of mystifying effects could be
performed. By matting out carefully selected portions of the pic-
ture, an actor could be placed in positions of apparently great danger,
heroically performing impossible feats. In some cases, too, the effects
could be further extended by judiciously animating the actor, much
as Mickey Mouse cartoons are animated today, and then superim-
posing the animated action upon conventionally photographed back-
grounds.

Thanks in no small measure to the achievements of such engineers
as A. S. Howell, for producing camera movements capable of un-
varyingly accurate registration, multiple-exposure work has expanded
to an amazing extent. In one such shot, made in the early days of the
talkies by J. P. Fulton, no less than 64 successive exposures were
made upon a single film. As the camera travelled about a cafe set,
the faces of each of 32 different men changed momentarily to that of
the hero. It is a tribute to the accuracy of the camera and to the
craftsmanship of the cinematographer that this highly intricate

296 F. W. JACKMAN [J. S. M. P. E.

problem of multiple matting, timing, and registration was accom-
plished perfectly on the first attempt.

In due time, various forms of multiple printing grew to supplement
and to a great extent to supercede multiple-exposure camera work.
Many systems have been evolved, used and patented. Among them
probably the best known is the Williams system, which involves the
use of complementary moving mattes. The actor works in front of
a blank background. From the shot, special negative and positive
mattes are made and so intensified that in one matte the figure is
simply a black silhouette against a clear background, while in the
other the figure-image is clear and the background opaque. The
mattes serve as masks through which in the first case the background-
shot, and in the second-case, the action, are double-printed on a
single film.

More recently a number of processes have been evolved in which the
background image is printed directly upon the negative of the action
by running a toned print of the desired background through the cam-
era in front of the unexposed film. The actors are illuminated by
light of the same color as the toned background plate and perform in
front of a plain background flat illuminated by light of a comple-
mentary color. This prints the toned positive image upon the raw
film in the camera, while the complementary colored light reflected
from the actors passes through the toned image as if the latter did
not exist. The Dunning process is perhaps the best known of these
systems, but quite a number of others have been evolved, used, and
patented; they differ mainly in details, such as the colors used, etc.

At present, virtually all composite shots are made by the projec-
tion background process, which is much simpler. A print is made of
any desired background scene, still or moving, which is projected
upon a large translucent screen of sand-blasted plate glass or cellulose,
placed behind the foreground set and action. The background pro-
jector and the camera that photographs the composite scene are elec-
trically interlocked so that the shutters open and close synchron-
ously.

It is obvious that any trace of unsteadiness in the projected picture
in this process will destroy the usefulness of the whole composite
scene. If the background plate is photographed in a camera that is
not absolutely steady, the background of the composite scene will
not be steady with relation to the foreground. If the background is
printed in a printer that does not register perfectly, the same effect

Sept., 1937] SPECIAL-EFFECTS CINEMATOGRAPHY 297

will result. If the projector does not maintain its registration micro-
scopically, there will again be unsteadiness; and if the foreground
camera is unsteady, this, too will be exaggerated in the composite.

The obvious solution is to use pilot-pin registration throughout —
from background camera through the printer, projector, and com-
posite taking camera. But that is only part of the answer. Modern
projection background work demands such exactly accurate registra-
tion that the pilot-pins must register through the same perforations
throughout each operation.

Motion picture photography is based upon the use of two types
of camera, the Bell & Howell and the Mitchell, both of which are
equipped with excellent pilot-pin registration systems. But one
registers through two perforations above the frame, while the other
registers two perforations below the frame.

Clearly, if we photograph the background with a camera employ-
ing one system of registration, and print or project it with equipment
employing the other system, we can not attain microscopically per-
fect registration in the projected picture. The error, viewed from a
production viewpoint, may be negligible, but it is ample to spoil a
process shot. For much the same reason certain designers of theatrical
projectors who have offered projectors for process work equipped with
side-tension registration only, have gravely underestimated the
problem. Such a projector will undoubtedly be abnormally steady
for theatrical use, but worthless for process purposes.

The writer has found the commercial answer to the registration
problem in the equipment designed and built for him by William
Matz, of Hollywood, using the Bell & Howell system of pilot-pin
registration throughout. Each unit is equipped with two interchange-
able movements : one for use with background-plates photographed
with the Bell & Howell camera, the other for use with Mitchell-
photographed backgrounds. Each has its registering pins working
through the same pair of perforations, in printing and projecting,
that were used in photographing the original background negative.

Equally important is the laboratory processing of both the original
background negative and the projection prints made from it. Abso-
lutely accurate control of gamma is necessary; fineness of grain is
most desirable; and for best results it is desirable that there be no
directional markings upon the film. Excellent results have been at-
tained in the author's plant with the Roto-tank developing system
engineered by Roy Davidge, which places the film upon a large metal

298 F. W. JACKMAN [J. S. M. P. E.

reel, sandwiched between spirals of a celluloid apron similar to those
used in developing miniature camera negatives. The reel is laid
horizontally in the tank, and oscillated 75 to 85 times per minute.
This gives a nondirectional turbulence that produces no measurable
directional markings, and furnishes a more clean-cut negative with
greatly improved shadow-detail. Quite incidentally, the method re-
duces the developing tune about 45 per cent, and permits diluting
the developer considerably. There is no strain on the film, so ex-
pansion and shrinkage are minimized.

Some idea of the extent to which the projection background proc-
ess is used today may be gained from the fact that in one important
picture now showing — Metro-Goldwyn-Mayer's Captains Courageous
— more than 80 per cent of the release footage was enacted before a
process screen. Although this is an outstanding sea story, not one
of the actors got nearer the ocean than a Culver City sound stage.
Perhaps 15 per cent of the footage consists of atmospheric long-shots
of the fishing boats; another 5 per cent, conventional intimate shots
of the players; the remainder of the picture, including virtually all
the important action, was filmed by means of projection background
"process shots."

Another important modern development is optical printing, which,
as is well known, consists essentially in rephotographing positive
prints of given scenes, frame by frame. Basically, the optical printer
consists of a light-source, a positive film-moving mechanism usually
using a specially modified Bell & Howell type of pilot-pin movement
and a camera-head, also equipped with accurate pilot-pin registra-
tion. Both Bell & Howell and Mitchell camera heads are used.
Both film movements are driven from a common power source, and
in most cases they may be operated at various speeds with relation
to each other. That is, they may operate either to expose one or
more frames of negative to each frame of positive, to skip alternate
positive frames, to hold a given positive frame motionless for any
number of negative exposures, or to reverse action by reversing the
direction of the positive's travel with relation to the negative.

In addition to making multiple-exposure and multiple-printed effects
under the most controllable conditions, the optical printer regularly
produces such transitions as fades, wipes, dissolves, turning-page
effects, and the like by means of travelling mattes and variable
optical elements.

Moreover, the optical printer often serves as a means of doctoring

Sept., 1937] SPECIAL-EFFECTS CINEMATOGRAPHY 299

ailing scenes. Vernon L. Walker has told of two such examples of
how his department's optical printing staff saved the studio the ex-
pense of retakes. In one picture an important scene was marred by
a truck that passed through carrying an objectionable advertising
sign. By means of the optical printer, the sign was blurred until it
became no longer noticeable. In another picture, the star was sup-
posed to crash in an airplane, escaping just as it caught fire and
burned. He dropped from the cockpit and crawled to safety as
scheduled, but the fire started too late, and did not burn to any ex-
tent until he had crawled out of the picture. As the plane was com-
pletely burned, a retake would have been expensive. The optical
printer effectively moved the explosion and the fire up to the ap-
pointed time at virtually no expense.

The miniature is one of the very earliest of camera tricks, but is
still of great importance today. Shots of ships at sea, naval battles
and disasters, zeppelins and airplanes, trains and train-wrecks, and
the like, are almost invariably photographed in miniature. Often
when it is desired to establish a location in an atmospheric long-shot
without necessarily using a stock-shot to establish the location as
some particular one, a miniature setting is used.

Making miniatures is far too complicated to be detailed here.
However, in practice it is almost a matter of applying a mathematical
formula : if the miniature is built to a certain scale, moved at a cer-
tain speed, photographed from a certain camera position, lens angle,
and camera speed, the result upon the screen can be predicted with
mathematical accuracy.

A miniature may be used as a projection process-background plate.
In some instances, actual scenes may also be projected into a minia-
ture, as was done in King Kong and other films.

Another important use of miniatures is in what are called "set
miniatures," in which parts of the set, sometimes foreground and more
often background, are made in miniature. If designed and lighted
in proper coordination with the design and full-scale photography of
the set itself, they can not be detected as miniatures, and enhance
considerably the illusion of size and depth, while effecting notable
economies.

It may be well at this point to correct the impression held by many
persons, even within the industry, that a miniature is necessarily
toy-sized. It is not uncommon for a large miniature set to cover a
complete stage and to be perhaps a hundred feet deep by forty or

300 F. W. JACKMAN U. S. M. P. E.

fifty wide. The miniature galleons referred to at the start of this
paper were 12 feet long with masts 16 feet high. In another impor-
tant miniature shot, the ship was so large that two men rode concealed
within to operate necessary mechanical devices, and it was yet neces-
sary to ballast the miniature ship with more than a ton of lead.

The motion of miniatures is sometimes effected by self-contained,
remotely controlled power units; but much more frequently minia-
tures will be moved and controlled by concealed or invisible wires,
permitting more accurate control. A miniature airplane, for instance,
may have an electrically driven propeller, but it is usually made to
take off, land, fly, and turn by invisible piano wires attached to the
wing-tips and tail and working through pulleys on a T-shaped sup-
port sliding along overhead wires.

How is all this special-effects engineering coordinated with the
regular operations of routine production? In the first place, the script
for the entire production is ordinarily submitted to the head of the
special-effects staff, who analyzes it and segregates the scenes that
can advantageously be done by his department.

With the scenes classified, he can then make accurate plans as to
how they can best be filmed. He prepares the plans and submits
them, with an itemized budget, to the studio production executives.
When the budget is approved, he sets up a schedule by which the
various special-effects scenes can be made that must coordinate with
the schedule for filming the regular scenes of the picture.

Generally speaking, the special-process scenes involving the actors
are scheduled for the end of a picture's shooting period. This, how-
ever, is all too often a very optimistic statement, for such scenes are
habitually used as covering shots for every conceivable emergency
from bad weather to the illness or injury of one of the principals. As
such, the production manager may suddenly call for making scenes
days or weeks before they are scheduled — and is usually surprised
if he finds that some other unit, working correctly to its own schedule,
is occupying the special-effects department's facilities when he so
unexpectedly demands them! There are also all the minor disturb-
ances common to all production routines. Story changes may over-
night remove process sequences one is prepared to shoot and replace
them with totally unexpected ones.

It is a tribute to the skill of all our studio' special-effects executives
and their staffs that in spite of all this, the quality of all kinds of

Sept., 1937] SPECIAL-EFFECTS CINEMATOGRAPHY 301

special-effects work has steadily improved, while the average cost
per shot has steadily decreased with each succeeding year. The
secret of this success is a matter of both knowledge and organization.
A properly conducted special-effects unit, whether a department in
a major studio or an independent special-effects contractor, must in-
evitably be an organization of many specialists. The men must be
specialists in much more than photography alone : practically every
phase of studio activity must be represented. In addition to the
stage crew of thoroughly competent operating and assistant camera-
men, electricians, carpenters, and grips, all experienced not only in
production but in special-effects technic, presided over by a trained
Special Process Cinematographer or Director of Special-Effects
Photography, there must be specialists in designing, building, and
painting miniatures and full-scale sets and props; molders, riggers;
art-directors, draftsmen, and the like. There must be laboratory
technicians skilled in negative and positive film development, printing,
multiple printing, optical printing, dye-toning and sensitometry.
There must be cutters, projectionists, and clerical workers, all of
whom know not only ordinary studio routines, but special-effects
work. Over all must be a thoroughly experienced chief who must be
at the same time a highly trained technician, a salesman, a director,
and an executive.

At his disposal must be not only the services of this varied and
highly skilled personnel, but also a plant ample to take care of the
physical requirements of the work. Finally, it is vital that he have
access to an ample library of background scenes — not ordinary stock
shots — from all over the world, accurately indexed and cross-indexed.

This matter of organization is what marks the final difference be-
tween the "black magic" pioneering days of special-effects cine-
matography and today's commercial special-effects engineering. The
early "trick cameraman" did much of his work almost single-handed.
Today's special-effects specialist could probably do so as well; but
he does not, because it is more efficient to utilize the advantages of
organization. Without such organization, special-effects cinema-
tography would still be possible, but it could not be the commercial
asset it is today.

In conclusion, the writer wishes to express his gratitude to the
persons and studios who have cooperated in preparing this paper
and the demonstration film; mentioning especially Byron Haskin
and Warner Bros. -First National Studios, Farciot Edouart and

302 F. W. JACKMAN

Paramount Productions, and Vernon L. Walker and R-K-O Radio
Studios.

DISCUSSION

MR. MORGAN: What has happened to the problem of "hot spot?"

MR. JACKMAN: A great deal of the credit for eliminating the "hot spot" must
be given to a commercial screen manufacturer who has done a great deal of work
on the subject. He has finally come to the conclusion that the "hot spot," or a
great deal of the "hot spot," is caused by light transmitted through the screen.
He has made a screen that I have been using during the past three or four years
that is very much denser than the screens used previously. A high amperage
is required, but there is very little difference in the temperatures, and I think
the worries over the "hot spot" are eliminated. Previously we did not have an
arc lamp that could handle the high amperage that is necessary, but I am now
using a commercial lamp that presents no difficulties at all in getting a steady
light up to 240 amperes.

MR. BOWERS: What, if any, work has been done with Technicolor back-
grounds?

MR. JACKMAN: We have done some processing in Technicolor with varying
results. It is easy to do airplane backgrounds, because we can take on enough
color from the coloring in the film; but we have been able to do regular back-
ground work with only small pictures, perhaps six to eight feet wide.

PRESENT ASPECTS IN THE DEVELOPMENT OF 16-MM.
SOUND-FILM*

A. SHAPIRO**

Summary. — A review of recent developments in 16-mm. sound, including techni-
cal advancements and perfections contributing to raising the standards of illumina-
tion and quality, and a discussion of the extent to which the limits of picture size and
audience have been raised for large-audience performances.

Adoption of the 16-mm. sound-film for education is discussed. Its function as a
medium of instruction for general education of an extra-curricular nature and its
use in the classroom as a corollary to text-book and oral instruction are treated.

The relation between the 35-mm. and 16-mm. branches of the industry is discussed.
What is the legitimate domain of 16-mm.? Limitation of both types of film, the
most effective fields for each, and the encroachment of 16-mm. upon the entertainment
field are brought out, and the possible effect upon the general trend of type of enter-
tainment pictures is indicated.

At the Spring Meeting of the Society held here two years ago, the
writer outlined the trends in 16-mm. projection with special reference
to sound. At that time it was predicted that the immediate expan-
sion of the 16-mm. sound market appeared to be in industry, education,
and in non-theatrical fields. It was pointed out that its use in small
theaters would require producer cooperation, without which extensive
use in this field would not be possible.

It is interesting at this date to note that the predictions made two
years ago are already on the way to realization. The sound picture is
today definitely recognized as an important factor in industrial public-
ity and advertising. The schools have accepted it as a valuable con-
tribution to curricular activities as well as for general educational
work. There is a growing use of 16-mm. sound as an entertainment
medium in the non- theatrical field.

The present-day types of 16-mm. sound-film and equipment show a
marked advance over the types available two years ago. Constant
improvements in laboratory processes have resulted in prints having

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
26, 1937.

** The Ampro Corporation, Chicago, 111.

303

304 A. SHAPIRO [J. S. M. P. E.

a wide range in frequency response. Equipment has been perfected
so that it reproduces this wide range with negligible distortion.
While illumination has been somewhat improved with the introduction
of higher- wattage lamps and better optical systems, by far the greatest
improvements have been in the increased volume and higher quality
of the sound reproduction. There are now available at least two rec-
ognized equipments that have power outputs of 40 watts or more,
suitable for the largest auditoriums, that are sufficiently compact
so as to be easily transportable and quickly set up for operation under
widely varying conditions. These improvements have made it possi-
ble to use 16-mm. sound in large auditoriums and halls that previously
could be satisfactorily taken care of only with 35-mm. As today's
improved illumination and sound have actually been designed for such
auditoriums and halls, the user is not limited to the small audiences
of yesterday.

For commercial and industrial purposes the use of 16-mm. sound has
almost entirely replaced 35-mm. There are now established a number
of film producers who specialize in supplying pictures for this field.
The pictures and sound are recorded on 35-mm. film in the usual man-
ner and then reprinted on 16-mm. film. Reprints of such pictures are
comparatively inexpensive and occupy one-fourth the space of 35-mm.
prints. This makes it possible to transport the equipment easily from
place to place, and set it up quickly for operation. Since no profes-
sional operators are required, the performances can be put on by sales-
men or company representatives.

The effectiveness of such presentations is now generally recognized
by industry. Among the largest users of this medium are the mem-
bers of the automotive industry. In this field 16-mm. sound drama-
tizes the stories of new models, tires, batteries, piston rings, etc.,
wherever there is a roof overhead and a crowd ready to listen. One
large automobile manufacturer has several hundred 16-mm. sound pro-
jectors constantly in the field dramatizing the story of its products
before dealers and prospective customers. The shows are staged
under all sorts of conditions, in dealers' display rooms, at club
meetings, and local auditoriums. Wherever an audience can be
brought together, 16-mm. sound is translating the advertisers' mes-
sages to interested groups.

The circulation possibilities of this kind of advertising are rather
startling. For instance, Pennzoil has a 16-mm. sound picture called
Farther, Faster, Safer which is a history of transportation development

Sept., 1937] DEVELOPMENT OF 16-MM. SOUND-FILM 305

in the United States condensed into twenty-five minutes of gripping
events in motive history. The picture has been shown to students,
business men, shop groups, service clubs, social organizations, and in
schools, colleges, and churches, to a total of more than 2,500,000 active
prospects for Pennzoil.

There is every reason to believe that the industrial field will enjoy
continued further expansion for 16-mm. sound. Its value as an adver-
tising medium is now well established, and its low cost compares favor-
ably with those of other established mediums. At the same time,
no other medium makes possible such a vivid dramatization of a
manufacturer's product as does the talking picture. The prospect's
entire attention is held in focus by the picture and, with the addition
of sound, is concentrated upon the sales story.

It is in the educational field, however, that the most interesting
developments have taken place with 16-mm. sound. Here the silent
film had already made large inroads. Educators had recognized that
the motion picture was a definite contribution in the field of pedagogy.
The interest in visual education had resulted in the development of
large libraries of educational film. Almost every subject taught in
our grade schools and high-schools had been picturized, and compre-
hensive film libraries had been developed. According to a tabulation
published in July, 1936, by the American Council of Education, which
covered only 9000 of the 242,000 schools in America, there were 6,074
16-mm. silent projectors in use in these schools. They also reported
having a total of 30,619 reels of 16-mm. silent film. As the investiga-
tions from which these figures were obtained covered only a small por-
tion of the schools of the country, it is quite evident that motion pic-
tures have found extensive use in education.

It is only natural that the educational field, having already found
the motion picture a valuable tool, should be tremendously interested
in the addition of sound to enhance its effectiveness further. Two
things were required before 16-mm. sound could find wide acceptance
in schools. First, there had to be equipment available, with the rela-
tive simplicity of the silent projector for easy and clear reproduction ;
second, an adequate sound-film library similar to the extensive silent
library now available.

In the early stage of this development, there was an inevitable delay
due to the fact that purchase of equipment was deferred until an ade-
quate library was produced, while the film producers were equally
reluctant to invest in large libraries until there was a sufficient quan-

306 A. SHAPIRO [J. S. M. p. E.

tity of equipment available to make use of such libraries. In this way,
there was a natural hesitation until enough machines and films were
produced to give the entire movement an initial momentum. Once
a substantial beginning was made, progress became extremely rapid,
and machines and films were produced in ever-increasing numbers.

One of the earliest producers of educational sound pictures on 16-
mm. films, was Erpi Picture Consultants, Inc., of New York, N.Y.
Their list of subjects now covers biological science, natural science
physical science, social science, music, teacher training, and psychol-
ogy. Most of these subjects are designed for high-school or college
work. Erpi Consultants are now preparing 16-mm. sound-films for
lower-grade work, and will undoubtedly continue to increase their
library at a greater rate. Other organizations also have entered into
the production of educational subjects so that a large library can be
confidently expected in the near future.

The increased use of talking pictures in schools has produced an in-
teresting development in school architecture. While it is not neces-
sary to build classrooms especially suited for showing talking pictures,
nevertheless much can be done to improve the effectiveness of the
presentations by providing suitable acoustics, means for properly
darkening the room, and proper arrangements of seats for good vision.
In a number of schools now being built through funds supplied by the
Works Progress Administration, some of the classrooms have been
designed so as to be especially adaptable to showing talking pictures.
This recognition is significant in that it illustrates the importance
with which the talking picture is now accepted by educators.

That the schools are fast becoming aware of the possibilities of 16-
mm. sound is illustrated also by the large numbers of courses for teach-
ers and prospective teachers in visual education. Courses are being
given not only in the technic of projector operation, but also in the
more advanced methods of correlating pictures with textbook and oral
instruction. It must be borne in mind that the use of talking pic-
tures in education differs from its use in entertainment in that in edu-
cation there is a fundamental learning process that takes precedence
over every other factor. Repetition is of great assistance in the learn-
ing process. The educational picture often required repetition of all
or portions of it, particularly to emphasize the more difficult phases of
the subjects being taught. In many cases the pictures are used as an
introduction to the subjects, as focal points for discussion, and as
means for reviews.

Sept., 1937] DEVELOPMENT OF 16-MM. SOUND-FILM 307

In the past it has been insufficiently realized that the primary prin-
ciple of the educational picture is to educate, and this resulted in edu-
cational pictures that had much more entertainment than educational
value. Sufficient experience has now been had to justify viewing this
problem from its primary function, that of a tool to increase the effec-
tiveness of the educational processes. Here, it seems, is a field in which
the pedagogue and the film producer can unite with great effective-
ness in making valuable contributions to the field of education.

Another phase of 16-mm. sound is its use in adult education and for
the dissemination of general and specific information. Among the
many Government bureaus that have adopted it for these purposes
are the Civilian Conservation Corps., the Department of The Inte-
rior, the Department of Justice, the National Park Service, the Naval
Air Station, the Post Office Department, the Veterans' Administra-
tion, the U. S. Naval Academy, the U. S. Department of Agriculture,
the Federal Housing Administration, the Tennessee Valley Authority,
and the National Archives. The demand for films by these many
agencies has caused the Government to become a producer in its own
right, and establish large staffs and well equipped studios for the
production of sound pictures. Practically all the pictures are reduced
to 16-mm. size for projection on 16-mm. portable equipment.

An interesting application in the field of political campaigning was
made in Sweden last year. The Peoples Party and the Socialist Party
were the foremost contenders for votes. Each put into the field a
battery of 16-mm. portable sound equipment that went barnstorming
throughout Sweden. That the voters appreciated this refreshing
change from the customary spellbinding is evidenced by the fact that
the interest in the election and the total number of votes cast was
greater than in any previous election. It is extremely gratifying to
us in America that the equipment used by both parties was of Ameri-
can manufacture.

The use of 16-mm. sound for entertainment in the home has thus far
been very limited. Lack of available rental films of suitable quality
has retarded expansion in this field. With adequate film libraries there
should be a vast market in the home field where picture programs
can be selected to suit small-group requirements.

We come now to the theatrical field. It had been expected that
with the improvement in the 16-mm. sound reproduction, this instru-
ment would be considered for use in small theaters of capacities of six
hundred persons or less. The past two years, however, have not

308 A. SHAPIRO [J. S. M. P. E.

shown a decided trend in this direction. Theaters, whether large or
small, running current productions, are still using 35-mm. equipment,
in spite of the unquestionable savings not only in the cost of initial
equipment, but in the cost of operation, cost of films, and their dis-
tribution.

In England, and in many other European countries, a number of
theaters operate with 16-mm. equipment. The British Gaumont
Corporation furnishes their current productions on both 35-mm. and
16-mm. film, and, consequently, the theaters using 16-mm. equipment
can show the same pictures as the theaters using 35-mni. equipment.
This is also true of several other countries in Europe where income is
important and the difference of cost between the two sizes of film
has a direct bearing upon whether or not a theater can operate
profitably.

The principal reason for the non-use of 16-mm. film in the theaters
of this country is that American producers as a whole are opposed to
issuing their pictures on 16-mm. film. The entertainment library in
this country is still very much limited to pictures made in the past, a
great many of which were produced five or six years ago, with inferior
recording equipment; and in reducing these pictures to 16-mm.
prints, the resulting sound leaves much to be desired. This lack of
suitable material, in the opinion of the writer, is the principal factor
in the slow growth of the entertainment film in 16-mm. sound.

In spite of this difficulty, however, a number of operators are using
16-mm. sound-film for paid entertainments. They are generally road-
men, who, like the industrial film user, carry their entire equipment
and film programs from place to place, putting on performances in all
sorts of halls and auditoriums. There is an insistent demand by these
operators for more and better material, and undoubtedly this demand
will ultimately be satisfied. Already, a number of distributing film
libraries have opened in various cities and are doing a thriving busi-
ness in the rental of films to such roadmen.

We come now to the relation between the 35-mm. and 16-mm.
branches of the industry. What is the legitimate domain of each?
What are the limits of utility of the two sizes of film and the most effec-
tive fields for each? A re-statement covering these points, in view
of recent developments, is in order.

In the field of industry, 16-mm. sound has definitely replaced 35-
mm., except for showing advertising films in theaters. This, however,
is of dwindling importance, as the paying public greatly resents having

Sept., 1937] DEVELOPMENT OF 16-MM. SOUND-FILM 309

advertising pictures foisted upon them as entertainment. In the
wider and more legitimate use by industry for private and promoted
distribution of their pictures to picked groups, the field is all with the
16-mm. film.

In education, the 16-mm. size had already been adopted before the
introduction of sound. Here 35-mm. is definitely confined to large-
auditorium installations where it is planned to run current productions
of entertainment film. For teaching purposes, education has defi-
nitely adopted the smaller film and recognizes 16-mm. sound as its
most important visual aid.

For adult education and propaganda the requirements are similar
to those of industry in that the same equipment must be used in many
locations of widely varying conditions. For such use, 16-mm. sound
is a natural selection.

In the theatrical field there is little likelihood that 16-mm. will re-
place 35-mm. in theaters until the large film producers agree to release
current productions at least shortly after their initial theatrical per-
formances. Should the large film producers relax their policy of with-
holding current releases, a tremendous outlet will develop for 16-mm.
sound. In a previous paper, it was pointed out that of the 15,000
theaters in America, about 70 per cent have capacities of 600 persons
or less. A great number of these smaller theaters could utilize 16-mm.
sound-prints provided current films were obtainable. Undoubtedly
the several thousand theaters operating on the borderline between
profit and loss could swing into the profit side with the economies possi-
ble with 16-mm. There is also the foreign market, which is particularly
suitable for 16-mm. sound, due to the fact that the average foreign
theater has a relatively small seating capacity and the shipping cost of
prints forms a considerable expense item. This could be reduced
greatly with the use of 16-mm. prints.

To summarize, it appears that the 16-mm. sound-film is adaptable
to a number of uses. The 35-mm. film is limited to theatrical use, es-
pecially to large theaters. In every other activity of motion pictures,
the advantages are with the smaller film. Considerable exploita-
tion has been done in the industrial field. The trend in schools is for
at least one equipment in each school, and the future will undoubtedly
see a large expansion in this field. Theatrical use of 16-mm. sound-
film depends upon the attitude of film producers who control current
productions towards releasing 16-mm. sound-prints.

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus and materials are held, in which various manufacturers of equipment describe and
demonstrate their new products and developments. Some of this equipment is de-
scribed in the following pages; the remainder will be published in subsequent issues
of the Journal.

IMPROVED NOISE-REDUCTION SYSTEM FOR HIGH-FIDELITY
RECORDING*

H. J. HASBROUCK, J. O. BAKER, AND C. N. BATSEL

A new method of noise-reduction for variable-width film recording has been
adopted by RCA and has been found to give excellent results. The recording
optical system has been modified to incorporate a double-mask shutter and the
galvanometer no longer receives biasing current.

The shutter and optical system are shown in Fig. 1. The shutter, the recording
aperture, and the associated lenses are incorporated in a single unit, which can
be removed at will and re-installed without loss of adjustment.

A schematic diagram of the optical system is shown in Fig. 2, where may be
seen the exposure lamp, condenser lens, aperture, shutter masks, aperture pro-
jection lens, galvanometer, slit converging lens, slit, ultraviolet filter, objective
lens, and film. It will be noted that the recording aperture is a negative of the
familiar triangular aperture used for biased galvanometer recording. The two
shutter masks are drawn together when current is applied from the noise-reduc-
tion amplifier. They separate when the current is reduced by the rectified signal.
Since the images of the masks are moved vertically on the mechanical slit by the
galvanometer, it is obvious that they must be parallel and perpendicular to the
slit; otherwise, there would appear an audio-frequency modulation in the shutter
portions of the sound-track. While this would not cause distortion, it is undesir-
able.

A comparison of the new symmetrical sound-track and the biased galvanometer
track is shown in Fig. 3. It will be noticed that in the shutter track there is a
change of recorded sound amplitude without displacement of either zero axis line.
The unmasking action can be seen in the outer portions of the track as the modu-
lation level increases.

A new feature of the optical monitoring system permits viewing both speech
modulation and noise-reduction action simultaneously. Increased light for moni-

* Presented at the Spring, 1937, Meeting at. Hollywood, Calif.; received
May 13, 1937.

** RCA Manufacturing Co., Cam den, N.J., and Hollywood, Calif.

310

NEW MOTION PICTURE APPARATUS

311

toring and sharper focusing upon the card make visible high intermittent fre-
quency peaks which have heretofore been difficult to see.

The ability to observe the performance of a noise-reduction system accurately
during recording has been found helpful. Interference between the speech wave
and the masking action, if it should exist, can be discovered quickly and corrected
without having to wait for the results of the day's work. These aids to operation
assure more consistently good recording.

In detail the method of monitoring is as follows: A portion of the output beam
from the galvanometer is intercepted near the plane of the mechanical slit, and
is reflected back. In this way a portion of the aperture is focused upon the moni-

FIG. 1. Shutter and optical system.

tor card. As shown in Fig. 4 movements of the shutter masks are seen as changes
in height of the light-spot. Vibrations of the galvanometer are indicated upon
the card by lateral movement of one edge of the light-spot. Three conditions are
illustrated: (a) without modulation and with shutter closed, (b) modulation 50 per
cent and shutter partly open, (c) modulation 100 per cent and shutter fully open.
In the two latter cases the arrows indicate the magnitude of the modulation.

With ultraviolet light for recording and printing, and because of the non-slip
feature of the RCA printer, it is possible to maintain "standby" or "squeeze"
lines approximately one and one-half thousandths of an inch wide on the film
without fogging in the print.

The noise-reduction amplifier gain is usually adjusted to make the shutter open
fully and clear of the track with 80 per cent modulation. As for the dynamic
characteristics of the shutter, the device is entirely controlled by the amplifier

312

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

current. When properly adjusted, the time required for opening, with a suddenly
applied signal fully modulating the sound-track, is 0.012 second. The remasking
is accomplished in 0.16 second. This extended closing time avoids shutter modu-
lation at low frequencies, as for example, when recording organ music. Under
such conditions poor quality could result were the closing made faster. For
class A push-pull the only limit to the speed of opening is the filtering of audio-fre-
quency components from the rectified current.

Fig. 5 is a schematic diagram of the shutter mechanism. The driving element
consists of a reciprocating motor having a moving iron armature of the inductor
type. This construction employs air-gaps of varying area instead of length, the
chief features being good linearity over larger displacements and freedom from

FIG. 2. Diagram of the optical system.

high negative stiffness. The armature is coupled by means of a flexible steel
cross spring to a pair of light-weight masks arranged to move in opposite direc-
tions when the armature is displaced. These masks are drawn together by cur-
rent from the noise-reduction amplifier during periods of no modulation, keeping
practically all light out of the mechanical slit. The amount of unmodulated
light reaching the negative sound-track is limited by the shutter masks, which
move apart when a signal is applied to the system. When the limit of travel is
reached and the shutter current approaches zero, the masks are in a position im-
mediately to re-enter the slit as the modulation is reduced. This particular di-
rection of current for operation is preferable. If the masks were opened by a ris-
ing current the travel would be excessive for conditions of overmodulation and the
closing would be delayed. The shutter can not be damaged by excessive modu-
lation levels since there is then the least current in its windings.

Uniform travel of both masks is assured by factory adjustment, and depends

Sept., 1937]

NEW MOTION PICTURE APPARATUS

313

upon the relative length of span of the cross-spring either side of center. If the
spring were longer on one side, that mask would move over a shorter distance.
Equalizing is done on an optical fixture by loosening the clamping screw and slid-
ing the spring in the required direction. The adjustment is then permanently
retained.

To provide the necessary overall linearity of the shutter it was necessary first
to determine over what range the armature alone would travel in a linear fashion.
The drive ratio to the masks was then established, knowing the required displace-
ment of the masks. It is obvious that the geometry of the cross-spring and
attached masks is such that after a certain distance the movement becomes non-
linear in such a manner that with uniform armature motion the mask travel

Print shutter Print

FIG. 3. Comparison of the new symmetrical

sound-track and the biased galvanometer

sound-track.

would be accelerated toward the end of the opening movement. A drive ratio
was adopted so that the acceleration would begin as the armature motion dimin-
ished. This increased the overall linear range. In Fig. 6 may be seen the open-
ing displacement with current, showing that the linearity is well within the
required limits.

Another design problem was that of sufficiently reducing the moving mass to
obtain a high natural frequency for the shutter, below which it would be controlled
by stiffness and its excursions strictly governed by the amplifier current. The
masks were made of duralumin and arranged to provide maximum coverage with
minimum actual area of surface. The mass of the masks and the stiffnesses of
the cross-spring and supporting hinges were proportioned to attain the desired
natural period and yet retain good sensitivity. The complete shutter is tuned to a
frequency of 140 cps. Damping is accomplished electrically by using heavy copper

314

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

spools for the coils. This, plus the fact that the shutter resonates at a frequency
well above the highest that can appear in the output current of the control amp-
lifier, prevents "bouncing" or overshooting of the masks.

One matter to which particular attention has been paid in the design of record-
ing equipment is that of phasing for speech. It has been well established that
the majority of speech waves and many sounds from musical instruments are not
symmetrical, having lesser amplitudes during the half-waves corresponding to

rarefaction of the air. This is because of
the construction of the human voice
mechanism. The lack of symmetry is
plainly revealed in a variable-width sound-
track. If proper care is not exercised
in phasing the recording channel from
microphone to galvanometer, including

(•) No modulation
Shutter cloied

Lamp

Modulation
Shutter opening 75>

(e) Modulation 100*
Shutter open

FIG. 4. Movements of the
shutter masks as seen on
monitor card.

Aperture
Imaging

Lens

FIG. 5. Diagram of the shutter
mechanism.

the noise-reduction amplifier, considerable interference can occur between the
speech wave and the masking action. The requirements vary slightly depend-
ing upon the type of track being made. For standard recording, the longer
peaks of a non-symmetrical wave should extend away from the noise-reduction
or shuttered portion of the sound-track. This applies also to biased galva-
nometer recording. The noise-reduction amplifier is then phased to rectify the
half of the wave containing the smaller amplitudes.

How this appears in the new shutter type of track is shown in Fig. 7. At the
left is an example of wrongly phased speech. The correct phasing is at the right.
It will be noticed that in the latter track the large peaks project toward the cen-

Sept., 1937]

NEW MOTION PICTURE APPARATUS

315

ter, where there is plenty of room, and away from the shutter or masked portions
where the clearance is maintained at a minimum.

Phasing speech for class A push-pull is not so important. With equal travel
of both shutter masks a non-symmetrical wave might, however, interfere on one
side of the track, depending upon the galvanometer polarity. It is possible and
practicable to increase the travel of one mask a predetermined amount by means
previously explained, to take care of average speech conditions, permitting the
noise-reduction amplifier to continue rectifying the small side of the wave. Other
methods have been proposed; for example, duplicate control amplifiers operating
on opposite halves of the wave and driving isolated shutter masks. Most of the

.10

FIG. 6. Displacement vs. current.

arrangements suggested made the entire system unnecessarily complex in return
for a negligible improvement.

Because of its inherent flexibility the new noise-reduction system can be used
with a wide variety of sound-tracks, including special forms for original recordings
as well as standard symmetrical track for release prints.

Using the twin mask shutter in conjunction with a standard galvanometer as
light-modulator, three different types of sound-track can be produced:

(2) Standard symmetrical variable-width.

(2) Class A push-pull variable-width.

(3) Variable-density squeeze-track.

Push-pull sound-film recording is gaining favor for original negatives, and of

316 NEW MOTION PICTURE APPARATUS

the available types the class A variable- width is considered preferable. Its ad-
vantages are total elimination, by cancellation, of sibilant distortion commonly
known as "zero shift," allowing, therefore, considerably wider latitude in develop-

FIG. 7. Incorrect (left) and correct (right)
phasing of speech.

ment of both negative and positive than can be tolerated with standard track;
and second, cancellation of any disturbances that might result from incorrectly
adjusted noise-reduction equipment.

DISCUSSION

MR . To WNSLEY : Will you explain by what means you accomplish proper phasing
of the voice ? Suppose we have a track that is improperly phased ; what was done
incorrectly in the recording to phase improperly? How are you sure you get the
track in the proper phase?

MR. BATSEL: The purpose of phasing the system in respect to a non-symmet-
rical wave is to prevent excessive clipping by the shutter as it opens up the track.

Phasing is accomplished by applying a non-symmetrical wave to the input of
the system, and observing on the visual monitoring card the deflection of the gal-
vanometer. Looking at the card from the position of the operator, the left-hand
side of the light-beam represents the outside or maximum width of the track.
Our practice in phasing the system is to have the long peaks of the non-symmet-
rical wave point to the right of the monitor card, which on the track is to the cen-
ter. The shutter amplifier is then phased to rectify this side of the signal. This
practice permits full track for the long peaks and reduces clipping by the shutter
as it backs out to clear the short half of the signal.

It is known that the pressure side of the sound-waves produces the long half-
cycle. By observation the microphone is likewise phased so that the long half-
cycle deflects the galvanometer to the right, as seen on the visual monitor.

TWO NEW FILMS FOR DUPLICATING WORK*
C. E. IVES AND J. I. CRABTREE**

(I) INTRODUCTION

It has long been recognized that duplicate negatives of sufficiently improved
characteristics would be of value in protection against loss through damage to
the original negative. Capstaff and Seymour1 in an earlier publication have
denned a perfect duplicate negative as one which would give prints identical
in every respect to those obtainable from the original negative. Since that time
two papers have been published2'3 giving the results of later work on photographic
materials for duplicating work and methods for their use.

Recent progress in the photographic emulsion field has made available new
duplicating positive and negative films that possess in a high degree the char-
acteristics most needed for making satisfactory duplicates, and excellent results
from the standpoint of quality and graininess have been obtained through their
use.

(II) THE DUPLICATING POSITIVE FILM

The Duplicating Positive (emulsion series 1365) consists of a yellow dyed
positive emulsion of medium contrast coated on a clear base.

As shown in the curves in Fig. 1 suitable emulsion quality and development
characteristics are obtained with the D-76 type of developer in the working gamma
range of 1.0-1.5. There is practically no fog under normal conditions of use.
It will be noted from the exposure scale that exposures somewhat greater than
usual have been employed. The Eastman lib sensitometer gives proper ex-
posures for process control purposes with multiple exposures of three to eight
times. The sufficiency of exposure under any particular condition can be judged
from the extent of the straight-line portion of the curve obtained. It is usually
found that a triple exposure is sufficient when the lib sensitometer is set for the
positive exposure condition with the exception that the light-filter is removed.
The color-sensitivity of the Duplicating Positive emulsion is similar to that of
Motion Picture Positive (series 1301) and, therefore, this film can be handled
under the positive room illumination furnished by the Series 0 Wratten safelight
in an indirect fixture.

(III) THE DUPLICATING NEGATIVE FILM

The Duplicating Negative Film (emulsion series 1203) consists of a low-
contrast panchromatic emulsion coated on a gray base of the same type as used
for other negative film.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 20, 1937.

** Eastman Kodak Co., Rochester, N. Y.

317

318

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

The curves in Fig. 2 show that with the D-76 type of developer, proper emulsion
quality and control of contrast are obtained in the recommended gamma range
of 0.6 to 0.7. Emulsion 1203 is exposed sufficiently when a single exposure is
given with the lib sensitometer at the normal positive setting.

The distribution of spectral sensitivity is shown by the spectrogram in Fig. 3,
the indications of which will be found useful for comparison with those of other
emulsions, as shown on page 64 of the handbook of "Motion Picture Laboratory
Practice."4 This extended color-sensitivity gives the Duplicating Negative
emulsion additional speed which is of considerable advantage where optical
printing is employed, and particularly in the case where a master positive is
dense. While the panchromatic emulsion is sensitive to all portions of the visible

300

a eo

260

22O

200
1.80

h I.6O
M

2 iao

. 100
.eo

60

ao
20

FIG. l(a). Exposure curves of Duplicating Positive
(emulsion 1365), with D-76 developer.

spectrum, the green Wratten Series 3 safelight has the advantage of visual
efficiency at the level of illlumination employed in photographic darkrooms.
However, the speed of the Duplicating Negative emulsion is such as to permit
illumination levels somewhat higher than are obtained conveniently by the use of
the standard Wratten Series 3 filter. The most satisfactory way of obtaining
the required increase in illumination is to substitute a sheet of tissue paper for
the regular-weight white paper used in the Series 3 filter. The darkroom illumi-
nation should be tested with the Duplicating Negative Film in the manner recom-
mended in the handbook of "Motion Picture Laboratory Practice"4 (p. 139).

It will be observed that both the Duplicating Positive and Duplicating Negative
have a very fine grain structure and give a somewhat transparent brownish
image. The effective density of such a deposit when printing by contact on
Motion Picture Positive Film is considerably greater than that indicated by

Sept., 1937]

NEW MOTION PICTURE APPARATUS

319

visual densitometry. Consequently, the printing -contrast under this condition
is greater than it appears to be by visual or densitometric comparison with a
Super X (emulsion 1227) negative, for example. The values for density were
determined with a visual densitometer, usually the Eastman densitometer. The
effect of this condition on densitometry and the selection of gamma values is
treated in more detail below.

Both the Duplicating Positive and Duplicating Negative are capable of re-
producing fine image detail.

(IV) MAKING THE MASTER POSITIVE

The master positive should be the first print made from the original negative
in order to serve as an insurance against loss of or damage to the original negative
during editing, cutting, or printing.

(a) Printing. — Good reproduction of tone in the duplicating process is assured

FIG. 1(6). Time-gamma curve of Duplicating
Positive (emulsion 1365), with D-76 developer.

if the exposure is selected in such a way as to utilize the region of proportional
reproduction indicated by the straight-line portion of the characteristic curve.
In this region the densities in the master positive bear a direct relation to those
in the original negative. While it is possible to obtain acceptable tone repro-
duction without confining exposures strictly within this range, the manner of
procedure in the two steps in the process must be determined by trial and error.
No simple systematic procedure can be prescribed. Therefore, it is assumed,
for the purpose of description in this paper, that the region of proportional
reproduction is utilized exclusively.

Printing exposure requirements for the master positive are illustrated in the
following example: An original negative having a maximum density of 1.40
required an exposure of approximately 400 meter-candle-seconds to produce the
required minimum density in the master positive of 0.70 at a gamma of 1.25
under recommended development conditions. This exposure is given in 0.12
second by a 500-watt 110- volt monoplane filament lamp operated at approxi-
mately 85 volts and located at a distance of 10 inches from the raw film. These
conditions refer to the case of contact printing at 15 feet per minute. The

320

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

exposure required depends, of course, upon the emulsion speed realized under
the actual development conditions for the Duplicating Positive.

If the means of controlling exposures in printing the master positive provides
regular log exposure increments from step to step equal to those used in the
equipment for exhibition release printing, then the printer settings for master
positive printing can be obtained from those found necessary for a "balanced"
release print made from the original negative. It is necessary only to establish
the exposure level which will produce a sufficiently high minimum density for
successful tone reproduction, that is, about 0.70. If this procedure is followed,
the scene to scene variations in density are largely disposed of and a minimum
of adjustment will be required in the succeeding operation to produce a duplicate
negative that has uniform printing quality.

When operating conditions are being selected for the duplicating process the
effect of an adjustment at any point in the procedure should be tested by carrying

UOO EXPOSURE

FIG. 2(o). Exposure curves of Duplicating Negative
(emulsion 1203), with D-76 developer.

the duplicating process through to completion. Results should be judged only
by examination of prints from the original and duplicate negative, because visual
examination of the Duplicating Film images may be misleading for the reasons
stated above.

As stated in previous publications,2'3 the duplicating process requires printing
equipment capable of giving good definition and uniformity of exposure. A
diaphragm or matte type of light control is to be preferred to one involving
change in lamp current and, consequently, changing quality of illumination.
However, the effect of moderate changes in lamp current upon photographic
contrast is not very serious with emulsions 1365 or 1203.

(b) Processing. — Duplicating work requires the use of the best possible
processing equipment in order to hold such imperfections as unevenness below
a tolerance limit. The print from a duplicate negative shows the accumulated
imperfections of four steps in processing as compared with two in the case of a
print from an original negative.

Sept., 1937]

NEW MOTION PICTURE APPARATUS

321

The curves shown above were obtained under the manufacturer's standardized
processing treatment8 with D-76 developer of normal strength. The D-76 type
of developer gives good tone quality and permits convenient control of develop-
ment velocity through modifications of the nature suggested in an earlier publica-
tion.6 These modifications are also discussed on page 90, et seq., of the handbook
of "Motion Picture Laboratory Practice."4 In most motion picture processing
machines a developer of somewhat less activity than normal D-76 is preferable.
Good results can be obtained by dilution to two-thirds strength, for example, or
as suggested in the publication referred to. In order to obtain the best processing
control, it is desirable both for the Duplicating Positive Film 1365 and the
Duplicating Negative Film 1203 that processing be carried on in a developer
maintained at a uniform degree of exhaustion and replenished to maintain a
constant rate of development.

In selecting gammas for the master positive and duplicate negative it is as-

FIG. 2(6). Time-gamma curve of Duplicating
Negative (emulsion 1 203), with D-76 developer.

sumed in general that no modification of quality is intended to be effected through
the use of the duplicating process. Such modifications are easily made but are
considered as the exceptional case.

In the experimental work on the new type of duplicating emulsions tests were
made on the effect of using a high gamma for the master positive and a low gamma
for the duplicate negative as compared with the use of equal gammas in the two
steps. Graininess was found to be less for the high-gamma-low-gamma method
than for equal gammas. This confirms previous work3 on other emulsions.
Master positive gammas between 1.1 and 1.5 were found suitable for the master
positive with duplicate negative gammas in the neighborhood of 0.6 to 0.7.
Recommendations are made below on the basis of a value of 1.25 for the master
positive. A higher gamma in the master positive has the effect of procuring
somewhat greater effective emulsion speed in the master positive stage and,
generally speaking, a corresponding increase in the exposure required for printing
the duplicate negative, because of the increased master positive density. For
this reason it is not found advantageous to use higher values for the master posi-
tive gamma.

The yellow dye is discharged very rapidly from the emulsion during develop-

322

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

ment. While it imparts a temporary coloration to the developer, it does not
impair the properties of the developer.

A good hardening fixing bath such as F-25 is suitable for use with emulsion
1365. In the fresh fixing bath, fixation is complete in 2 minutes. Hardening
of this emulsion takes place rapidly and becomes excessive if treatment is pro-
longed greatly beyond this time. This should be avoided because the emulsion
surface is water repellent and, therefore, liable to water spotting. If, because
of necessarily longer time of treatment or because of the constitution of the fixing
bath, hardening is excessive, this should be corrected by suitable modification
of the bath.7'8 Fixing baths in an extremely exhausted condition should not
be used for duplicating work.

Hypo and other soluble substances are removed rapidly from the 1365 and
1203 types of emulsions during washing. On account of the value of any master
positive or duplicate negative as a permanent record, the washing should reduce
the concentration of hypo should be reduced to a very low magnitude by thor-
ough washing so as to avoid the danger of image fading.9

(c) Drying. — On account of the smooth glossy condition of the surface of
emulsions 1365 and 1203 and the inherent rapidity of drying, any maladjustment

FIG. 3.

Spectral sensitivity of Duplicating
Negative Film.

in the drying operation can cause drying spots. The quantity of "loose" water
left on the emulsion surface after squeegeeing must be very slight or droplets
form with drying lines or spots as a consequence. However, a careful adjustment
of standard squeegeeing equipment should suffice to give good results. The
1365 and 1203 emulsions are dried in one-third to one-half the time required for
Motion Picture Positive Film under the normal drying conditions for the latter.
The drying rate should be diminished by lowering the dry-bulb temperature, or
reducing the air velocity, or by raising the humidity in any convenient manner.
Upon leaving the drying cabinet, the film should be in a suitable condition for
handling in succeeding operations and, consequently, should have a moisture
content of equilibrium with an atmosphere of about 60 per cent relative humidity
at room temperature. This condition should be attained in about 15 minutes
of drying time.

(V) MAKING THE DUPLICATE NEGATIVE

(a) Printing. — As indicated above for the master positive, it is assumed that
the 1203 duplicate negative is to be exposed in such a way as to utilize the region
of proportional tone reproduction characterized by the straight-line portion of
the density-log exposure curve. For a master positive having a maximum den-
sity of 1.95, an exposure of 150 meter-candle-seconds is required to produce the

Sept., 1937] NEW MOTION PICTURE APPARATUS 323

minimum density of 0.45 at a development gamma of 0.65. These values have
been determined for the use of a master positive of the density and contrast
recommended above. The resultant duplicate negative will have a maximum
density of 1.30, a minimum density of 0.45, and a density scale of 0.85 as com-
pared with 1.40, 0.40, and 1.0 for the corresponding values in the original nega-
tive. The difference in the density scale of the original and duplicate negatives
results from the difference in the visual and effective printing densities of the
Duplicating Negative Film. This type of discrepancy is observed with duplicate
negatives made with materials used previous to the present time, but is of lesser
magnitude. However, it has no disturbing effect in the duplicating operation
after standards are once set up for the processing solutions which are used. Con-
trol in making the duplicate negative is maintained by means of sensitometric
strips exposed on the 116 sensitometer in the manner indicated above.

In establishing the standard operating conditions the use of a typical set of
data as shown in Table I should be convenient. It will be noticed that the gamma

TABLE I

Exposure and Development Data

Minimum Maximum Density

density density scale

Original Negative 0.40 1.40 1.00

Master Positive 0.70 1.95 1.25

Printed on Emulsion 1365

Step Printer: 15 Ft. per Min.

500-watt lamp : 85 volts

Meter-Candle-Seconds: 400
Developed in D-76d, 2/s strength,

70°F. 43/4 Min.
Gamma: 1.25

Duplicate Negative 0.45 1.30 0.85

Printed on Emulsion 1203

Step Printer: 15 Ft. per Min.

500-watt lamp : 60 volts

Meter-Candle-Seconds: 150
Developed in D-76d, 2/3 strength,

70°F. 3V» Min.
Gamma: 0.65

product obtained from the master positive and duplicate negative gammas
(lib sensitometer), which might have been expected to be unity, is actually
about 0.81.

If local conditions favor the use of other developers or different gammas at
either step in the process, then control values should be determined for those
conditions by carrying test samples through the complete duplicating process.
Adjustments should be made in one step or the other until proof prints from the
original and duplicate negatives developed together indicate equal effective
printing contrasts in those negatives.

324 NEW MOTION PICTURE APPARATUS [J. S. M. p. E-

If it is considered advisable to utilize portions of the density-log exposure
characteristic lying outside the straight-line portion, then new standard control
conditions must be adopted. When a change of this kind is made in the master
positive exposure, then compensatory changes in the development of the master
positive and the duplicate negative and in the exposure of the duplicate negative
are necessary, if an acceptable reproduction of tone is to be retained.

In working out the new conditions discussed in the preceding paragraph, a
density step-tablet should be attached to the original negative and should be
reproduced with picture tests in all succeeding steps. Prints from the tablets
in the original and duplicate negatives will furnish data for reproduction curves
prepared in the manner suggested in a previous paper.3 A more complete
analysis of the effect of changes in procedure in any step can be obtained through
the use of a method for the study of tone reproduction described by L. A. Jones.10

As stated in connection with the printing of the master positive, the printing
equipment must be capable of giving uniform exposure and good definition. It
is anticipated that the process of printing the duplicate negative will frequently
involve optical printing and that it may be required to produce duplicate nega-
tives of equal quality by optical and contact printing. With optical systems
where illumination is strongly specular the contrast obtained in projection
printing is greater than that in contact printing. When printing from a 1365
master positive this increase in contrast may not be of the same magnitude as
with materials previously used. It may be necessary, therefore, to make an
adjustment in the development contrast of the duplicate negative or to modify
the illumination system of the optical printer in the manner described by Tuttle
and Young11 in order to obtain the required agreement in contrast. As stated
previously, the printing contrast of a duplicate negative must be judged from
the prints which it yields in comparison with prints from the original negative.

When the negative is exposed in such a way as to utilize the straight-line por-
tion of the Duplicating Negative characteristic, the duplicate negative will
usually have greater effective printing density than an original negative in which
very low densities are found.

(b) Processing. — As in the case of the Duplicating Positive, a modification
of the D-76 developer can be used to advantage. Unless the development gamma
for the duplicate negative is greatly different from that recommended, the same
developer can be used as for the master positive. If a different developer activity
is required for this or other reasons, it can be obtained in the manner suggested
previously.

The developer used for Duplicating Negative Film should not be permitted
to vary greatly in its exhaustion level. If it is attempted to compensate for
extremely different degrees of exhaustion by varying the time of treatment, the
image color may be affected in such a way as to alter the effective contrast for
a stated development gamma.

In a fresh fixing bath of the F-25 type, emulsion 1203 is fixed completely in 4
minutes. As recommended previously, necessary steps should be taken to avoid
excessive hardening.

Sept., 1937] NEW MOTION PICTURE APPARATUS 325

(VI)GENERAL RECOMMENDATIONS

A duplicate negative is acceptable for release printing only if scratches, abrasion
marks, dirt spots, and unevenness in density accumulated throughout the process
are held to the lowest possible amount by the exercise of due care in handling
and processing operations. It is recommended, therefore, that all necessary
aids to better processing such as those involving supplemental agitation in the
developing bath and the use of an acid stop-bath be adopted.

Cinching can be diminished by carrying out all winding operations in sufficiently
moist clean air and by winding firm rolls. Duplicating films show finger prints
and other handling marks rather prominently on account of the smooth glossy
emulsion surface.

Cleaning operations should be carried out in such a way as to avoid solvent
spotting or the condensation of atmospheric moisture. Also, attention should
be given to the equipment used for cleaning and to the choice of cleaning pads.

REFERENCES

1 CAPSTAFF, J. G., AND SEYMOUR, M. W. : "The Duplication of Motion Picture
Negatives," Trans. Soc. Mot. Pict. Eng. (Feb. 1927), No. 28, p. 223.

2 IVES; C. E., AND HUSE, E.: "Notes on Making Duplicate Negatives,"
Trans. Soc. Mot. Pict. Eng. (1928), No. 34, p. 382.

3 CRABTREE, J. I., AND SCHWINGEL, C. H.: "The Duplication of Motion
Picture Negatives," /. Soc. Mot. Pict. Eng., XLX (July, 1932), No. 1, p. 891.

4 "Motion Picture Laboratory Practice and Characteristics of Motion Picture
Film," Eastman Kodak Company (1936), 310 pp.

6 JONES, L. A., RUSSELL, M. E., AND BEACHAM, H. R.: "A Developing Ma-
chine for Sensitometric Work," /. Soc. Mot. Pict. Eng., XXYIII (Jan., 1937),
No. 1, p. 99.

8 CRABTREE, J. I., AND CARLTON, H. C.: "Some Properties of Fine-Grain
Developers for Motion Picture Film," Trans. Soc. Mot. Pict. Eng., XIII (1929),
No. 38, p. 406.

7 CRABTREE, J. I., AND HARTT, H. A.: "Some Properties of Fixing Baths,"
Trans. Soc. Mot. Pict. Eng., XIII (1929), No. 38, p. 364.

RUSSELL, H. D., AND CRABTREE, J. I.: "An Improved Potassium Alum
Fixing Bath Containing Boric Acid," J. Soc. Mot. Pict. Eng., XXI (Aug., 1933),
No. 2, p. 137.

8 CRABTREE, J. I., PARKER, H., AND RUSSELL, H. D. : "Fixing Baths and Their
Properties." (To be published.)

9 CRABTREE, J. I., AND Ross, J. F.: "A Method of Testing for the Presence
of Sodium Thiosulfate in Motion Picture Films," /. Soc. Mot. Pict. Eng., XTV
(April, 1930), No. 4, p. 419.

10 JONES, L. A. : "On the Theory of Tone Reproduction with a Graphic Method
for the Solution of Problems," /. Soc. Mot. Pict. Eng., XVI (May, 1931), No. 5,
p. 568.

11 TUTTLE, C., AND YOUNG, D. A.: "Illumination in Projection Printing of
Motion Pictures," J. Soc. Mot. Pict. Eng., XTX (July, 1932), No. 1, p. 842.

INFRARED NEGATIVE AS APPLIED TO SPECIAL-EFFECTS
PHOTOGRAPHY*

G. W. HOUGH AND W. LEAHY**

In the early part of 1935 the Agfa Ansco Corporation, responding to a general
demand by the motion picture industry for wider specialization of film products,
manufactured and marketed an infrared-sensitive negative material designed
principally for the purpose of photographing night effects in the daytime. Dis-
semination of technical information pertaining to the practical application of 1 his
product was undertaken, and the film gave promise of supplying the means of
eliminating, to a certain extent, the economic disadvantage of actual night photog-
raphy.

Production use, however, brought to light emulsion characteristics that, al-
though of decided utility in certain phases of motion picture work, did not lend
themselves well to the more intimate details required when photographing close-
ups of characters in standard panchromatic make-up.

As a direct result of this experience a new infrared negative, referred to as Type
B, was brought forth in December, 1936, and has, since that time, fulfilled all film
requirements necessary to the successful production of night scenes in the day-
time.

The physical properties of this new material, such as base and anti-halo treat-
ment, are similar, of course, to those of all motion picture negative films. It has
been designed to meet standard laboratory processing requirements, and the
keeping quality, under ordinary storage conditions, has proved to be excellent.

In general speed the film is nearly equal to that of Superpan when both types
are exposed without filters. It is necessary, however, in order that infrared-sen-
sitive negative fulfill the function for which it is designed, to expose only with red
filters which absorb the blue rays. Practical experience has indicated that the
most useful range of filters lies between the Wratten Monobrom 21 and the 29 F.
The filter-factor for these blue-absorbing and red-transmitting filters has been
found, by sensitometric and practical tests, to be from four to five. The use of
deeper red filters adds in no way to the pictorial quality and merely prolongs the
time of exposure. In many instances, however, filters as light as the Wratten
15G have been found suitable, although they transmit some ultraviolet in the
region of 3000 A.

Fig. 1 is a wedge spectrogram comparison of Superpan, the original infrared
type, and the new Type B infrared, and illustrates the characteristic color-re-
sponse of each material. Attention is pointed to the red and infrared-sensitivity
of the Type B material, which reveals a maximum at approximately 7400 A. The
sensitizing pattern of this type permits the use of relatively light red and even
heavy yellow filters, due to the lack of response in the green-yellow regions.

*Presented at the Spring, 1937 Meeting, at Hollywood, Calif. ; received May
15, 1937.

**Agfa Ansco Corp., Pacific Coast Technical Division, Hollywood, Calif.
326

327

Fig. 2 shows graphs of sensitometric time-gamma curves comparing Superpan
and the new Type B infrared negative, and reveals the comparable ratio of con-
trast obtained with these two types at various developing times. This similarity
is particularly desirable when photographing close-ups or when it is necessary to
match scenes photographed on regular panchromatic negative.

Principles of lighting technic pertaining to booster lights ordinarily employed
in producing night effects in the daytime, have been found entirely applicable
when using this type of film in conjunction with appropriate filters. Exhaustive
tests conducted to observe the effect of panchromatic make-up, reveal that the
only alteration necessary is a slightly darker lip rouge produced by the addition
of a small amount of blue or brown pigment.

Set practicals such as street lamps, automobile headlights, etc., are rendered

FIG. 1. Spectrogram comparison of (A) Superpan negative; (B) the origi-
nal infrared type; and (C) the new Agfa Type B infrared.

far more realistic than has heretofore been possible with ordinary panchromatic
film. Window lighting must be done, of course, with the aid of artificial lights,
as in the past, but reveals a far more sturdy effect. The use of either reflectors or
booster lights for close-up modelling has been found to be entirely satisfactory,
producing soft halftones with the required contrast when applied in the same
proportion as for panchromatic negative.

Pictorial long shots in which there is considerable green foliage are recorded
with particular charm due to the infrared reflection of chlorophyll, the green color-
ing matter of plants and leaves. The effect produced by this substance in con-
junction with this type of film when viewed upon the screen is very similar to that
viewed actually on moonlight nights.

328

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

Superpan Negative

toy Relative Exposure

Superpan Negative

with Blue -extinction filter

tl4««7**W

Lay Kf/ativf Expoturt

Infro R,d,lyp,B

Developed in 617

ln<ra Red, tifpt B

E«poHd ..tl. Blue Erti-dio"

f.lter. De^loped in B 17

ioy *»*»«/« frpctur* Log Ktlatht l*poturt

FIG. 2. Sensitometric time-gamma curves comparing Superpan and the new
Type B Infrared film.

2.4

1.2

<O IS* to' 25

Developing Time

Infra Red, type B
Developed in B-17

I 2345678-9

£oy Relative Exposure

FIG. 3. Exposure and fog curves of Type B Infrared film.

Sept., 1937] NEW MOTION PICTURE APPARATUS 329

Haze penetration properties, due to atmospheric absorption of short-wave
length radiation and the recording of the longer rays, make it possible to photo-
graph scenes of extreme beauty under what would ordinarily be regarded as ad-
verse conditions. Many economic possibilities have been exploited by pro-
ducers, who have long recognized the financial disadvantage and artistic short-
comings of night shooting. In numerous instances the intelligent application of
this new medium has not only resulted in a saving of light and labor, but has cir-
cumvented, as well, the ever-present danger of illness to important players when
heavy night schedules are necessary. This general utilization has included paint-
ing permanent street sets a blue-gray color so that a more realistic night effect
could be produced with infrared negative which, at the same time, would not
hinder the use of panchromatic for the day scenes.

Infrared negative involves no laboratory problem, as processing may be carried
out in the usual manner without special treatment or alteration in developing
times. The time-fog density curve shown in the upper left-hand corner of Fig. 3
reveals only a slight increase of fog with extended developing times. The ordinary
green safelight in general use for processing panchromatic film, although trans-
mitting some infrared rays, has been found by practical experience to be satis-
factory with the usual precautions.

In conclusion it is hoped that this addition to motion picture film material will
stimulate and encourage the imagination of the practical technician so that in the
future he will more readily demand of the manufacturer other special types en-
abling him not only to enhance the beauty of his productions but also to overcome
successfully the technical problems still awaiting solution.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D. C.,
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

American Cinematographer

18 (July, 1937), No. 7

Hessercolor Is All Set to Enter Still Market (p. 273). G. BLAISDELL
Reeves Combines Light Tester and Sensitometer

(p. 282).

Bell & Howell Installs Vaporate Film Treatment
(p. 299).

Electronics

10 (July, 1937), No. 7

Standards in Television (p. 10). H. M. LEWIS

The Resonoscope (p. 17).
Amplifier Measuring Technic (p. 18). E. F. KIERNAN

Filmtechm'k

13 (June 15, 1937), Nos. 9/10

Das Einmaleins des Rechnens in Dezibel, Phon und
Neper (A Table of Computations in Decibels, Phons
and Nepers) (p. 91). P. HATSCHEK

International Photographer

9 (July, 1937), No. 6
Color (p. 5). E. GIBBONS

International Projectionist

12 (June, 1937), No. 6
Typical Troubles in Modern Sound Reproducing

Units (p. 7). L. CHADBOURNE

Aligning the Lamp House with the Projector Mecha-
nism (p. 19). A. C. SCHROEDER

Journal of the Optical Society of America

27 (July, 1937), No. 7
Theory of Three-Color Reproduction (p. 227). C. HARDY AND

F. L. WURZBURG, JR.
330

CURRENT LITERATURE 331

Experimental Determination of Photographic 'Density

(p. 241). A. KOERNER AND

C. TUTTLE

Kinotechnik

19 (June, 1937). No. 7

Filmgerate in Osterreich (Austrian Film Apparatus)

(p. 148). P. SCHROTT

Die Geschichte der Bildwechselzahl (History of Image

Frequency) (p. 153). F. P. LIESEGANG

Die Eurocord-Tonkamera (Eurocord Sound Camera)

(p. 155). H. FREESE

Die Bedeutung der Normstimmung fur Musikauffiihr-
ungen, Tonaufnahme und Tonwiedergage (The Sig-
nificance of Standard Agreement on Musical Regis-
tration, Sound Recording, and Sound Reproducing)
(p. 159). O. FRANK

Negative-Entwicklung nach Proben oder mit kon-
stantem Gammawert? (Shall Negatives Be Developed
According to Tests or to a Constant Gamma Value?)
(p. 161). L. KUTZLEB

Fortschritte der Hochfrequenzkinematographie (Prog-
ress in High-Speed Motion Picture Photography)
(p. 164). R. THUN

Ein Vorbote des Plastischen Farbentonfilms (A Fore-
runner of Stereoscopic Color Sound-Films) (p. 165). L. KUTZLEB

Proceedings of the Institute of Radio Engineers

25 (June, 1937), No. 6
Television in Great Britain (p. 697). N. ASHBRIDGE

BOOK REVIEW

Mein Weg mit dem Film (My Experiences with Film) : Oskar Messter, Max

Hesse Verlag, Berlin-Schoneberg, 1936 (150 pp.).

This book was written at the request of Oskar von Miller to form a foundation
for the collection of historical data and apparatus that Messter gave to the Ger-
man Museum in Munich. A short historical resume of the work of Edison, Lu-
miere, Anschutz, the Skladanowsky brothers, and others prefaces the book.

The name of Oskar Messter has been connected with the German motion pic-
ture industry since its beginning, and there are very few branches to which Mess-
ter has not contributed.

As early as June 3, 1896, Messter built and sold his first projector. In the same
year he built his first camera, and because he was unable to obtain film, he used
8-exposure Kodak film which he slit to a width of 35-mm.

After his first cameras had been built, Messter designed and built the first under-
cut gate to protect the film from scratches. For the film movement he built a
four-part Maltese cross instead of using the 5- and 7-part cross which had been
used up to this time. As early as 1900 he built a working model of a projector
using mirrors to produce an optically intermittent movement.

In 1916 he obtained a patent on a variable shutter, and later on a camera with
an automatic device for fades and dissolves.

In 1896 he constructed a film perforator which perforated 120 frames per min-
ute. For his first developing outfit he built a drum having a capacity of 60 feet
of film, and later designed a processing machine for continuous developing, fixing,
and washing.

He obtained a patent in 1900 for an optical printer for trick work. To keep
the negative and positive in good contact, air pressure was used in the gate.

As early as 1897 he built and sold a projector using 35-mm. film which exposed
pictures along each half of the film width. It was used for amateur and teaching
purposes.

A patent was granted to him for synchronizing a player-piano with the projec-
tor. He employed a musical director to write music to accompany the film, and
in 1903 started work on synchronizing a gramophone with the projector. More
than 500 theaters were equipped by 1913 with this apparatus.

Messter became greatly interested also in color photography, and built a camera
with three lenses in 1898. To get slow-motion photographs he also designed a
high-frequency camera. His first camera was capable of taking 64 frames per
second. Later he built special cameras for Krupp for bullet photography, as well
as cameras for recording instruments on aeroplanes.

During the War he constructed cameras for time-lapse photography from the
air. He also built a camera of the machine-gun type for aerial shooting practice.

Besides these extensive activities he owned and operated a motion picture
studio, where he made his first releases, each 18 meters in length. His first studio
was opened in November 1896. It was independent of daylight, and used four
arc lamps (50 amp.) for illumination.
332

BOOK REVIEW 333

The actors were his friends and members of his family, and later members of
the opera and theaters were used in the casts. While these short films were be-
ing produced Messter worked diligently to improve his cameras and projection
equipment.

The slow evolution of the industry is carefully presented in the book with the
aid of many pictures and diagrams. The sections dealing with early work in
sound recording are especially interesting. This book represents a valuable con-
tribution to the historical development of the industry, and should be read by
those interested in the growth of the motion picture.

A. K. WlTTMER

COMMITTEES

of the
SOCIETY OF MOTION PICTURE ENGINEERS

(Correct to Aug. 20th; additional appointments or changes may be made at
any time during the year as necessity or expediency may require.)

L. W. DAVEE
H. GRIFFIN

A. N. GOLDSMITH
A. C. HARDY

ADMISSIONS AND TRANSFERS

G. FRIEDL, JR., Chairman
S. HARRIS
D. E. HVNDMAN

BOARD OF EDITORS

P. J. LARSEN
M. W. PALMER

J. I. CRABTREE, Chairman

L. A. JONES H. G. KNOX

E. W. KELLOGG T. E. SHEA

COLLEGE COURSE IN TECHNICAL MOTION PICTURE EDUCATION
T. E. SHEA. Chairman

A. N. GOLDSMITH

L. A. JONES

W. H. CARSON
O. O. CECCARINI

COLOR

J. A. BALL, Chairman
C. H. DUNNING
R. M. EVANS

A. M. GUNDELFINGER

H. W. MOYSE

H. GRIFFIN

J. H. KURLANDER

CONVENTION

W. C. KUNZMANN, Chairman

P. MOLE K. F. MORGAN

M. W. PALMER

H. WARNCKE

EUROPEAN ADVISORY COMMITTEE

J. VAN BREUKELEN, Chairman

F. H. HOTCHKISS I. D. WRATTEN

EXCHANGE PRACTICE

A. W. SCHWALBERG, Chairman

O. C. BINDER K. C. KAUFMAN N. F. OAKLEY

A. S. DICKINSON J. S. MACLEOD H. RUBIN

G. K. HADDOW H. A. MERSAY J. H. SPRAY

334

COMMITTEES OF THE SOCIETY

335

J. E. ABBOTT
T. ARMAT

HISTORICAL

E. THEISEN, Chairman
G. A. CHAMBERS
W. CLARK

G. E. MATTHEWS
T. RAMSAYE

O. B. DEPUE

A. N. GOLDSMITH

A. C. HARDY

MUSEUM

(Western)

E. THEISEN, Chairman
J. A. DUBRAY

HONORARY MEMBERSHIP

J. I. CRABTREE, Chairman

JOURNAL AWARD

A. REEVES

E. A. WILLIFORD

E. A. WILLIFORD, Chairman

E. HUSE G. F. RACKETT

L. A. BONN
R. M. EVANS
G. GIBSON
E. HUSE

D. P. BEAN
F. E. CARLSON
W. B. COOK
H. A. DEVRY

C. N. BATSEL
L. N. BUSCH
O. O. CECCARINI
A. A. COOK
L. J. J. DIDIEE
C. FLANNAGAN

J. E. ABBOTT
J. I. CRABTREE
A. S. DICKINSON

LABORATORY PRACTICE

D. E. HYNDMAN, Chairman

T. M. INGMAN H. W. MOYSE

C. L. LOOTENS J. M. NlCKOLAUS

R. F. MITCHELL W. A. SCHMIDT

J. H. SPRAY

NON-THEATRICAL EQUIPMENT

R. F. MITCHELL, Chairman

E. C. FRITTS R. C. HOLSLAG

H. GRIFFIN J. H. KURLANDER

J. A. HAMMOND

A. SHAPIRO
A. F. VICTOR

PAPERS

G. E. MATTHEWS, Chairman

M. E. GILLETTE E. C. RICHARDSON

E. W. KELLOGG F. H. RICHARDSON

W. A. MACNAIR P. R. VON SCHROTT

R. F. MITCHELL H. C. SILENT

W. A. MUELLER H. G. TASKER

I. D. WRATTEN

PRESERVATION OF FILM

J. G. BRADLEY, Chairman

R. EVANS T. RAMSAYE

M. E. GILLETTE V. B. SEASE

C. L. GREGORY W. A. SCHMIDT

336

COMMITTEES OF THE SOCIETY

[j. s. M. P. E.

MEMBERSHIP AND SUBSCRIPTION

E. R. GEIB. Chairman

Alabama

Michigan

Ohio

P. A. KING

J. F. STRICKLER

C. C. DASH

R. H. GILES

California

Minnesota

V. C. WELMAN

J. O. AALBERG

C. L. GREENE

C. W. HANDLBY

R. H. RAY

Pennsylvania

E. HUSE

H. BLOOMBERG

R. H. MCCULLOUGH

Missouri

A. GOODMAN

G. A. MITCHELL

]. S. COPLEY

I. SAMUELS

P. MOLE

K. F. MORGAN

New York

Texas

W. A. MUELLER

A. BECKER

H. H. FRASCH

H. G. TASKER

F. E. CAHILL

A. A. COOK

District of Columbia

Georgia

A. S. DICKINSON

H. T. COWLING

N. WEIL

J. J. FINN

R. EVANS

J. FRANK, JR.

N. D. GOLDEN

Illinois

S. HARRIS

F. J. STORTY

H. A. DEVRY

D. E. HYNDMAN

B. J. KLEERUP

W. H. INGRAM

Travelling

S. A. LUKES

O. E. MILLER

E. AUGER

C. G. OLLINGER

F. H. RICHARDSON

C. BRENKERT

J. M. SCHAEFER

P. D. RIES

F. HOHMEISTER

J. H. TOLER

C. J. STAUD

W. C. KUNZMANN

L. M. TOWNSEND

D. McRAE

Massachusetts

J. S. WARD

O. F. NEU

J. S. ClFRE

H. H. STRONG

S. SUMNER

Japan

A. B. WEST

T. NAGASE

Germany

Y. OWAWA

W. F. BIELICKE

Australia

H. C. PARRISH

New Zealand

Hawaii

C. BANKS

L. LA CHAPELLB

Austria

P. R. VON SCHROTT

England

Holland

W. F. GARLING

J. VAN BRBUKELBN

Canada

R. G. LlNDERMAN

F. C. BADGLEY

E. McMASTER

India

G. H. BATTLE

R. TERRANEAU

G. D. LAL

C. A. DENTELBECK

H. S. MEHTA

B. E. NORRISH

France

M. L. MISTRY

L. J. DIDIEB

China

L. G. EGROT

Russia

R. E. O'BOLGER

F. H. HOTCHKISS

E. G. JACHONTOW

Sept., 1937]

COMMITTEES OF THE SOCIETY
PROGRESS

337

L. N. BUSCH
G. A. CHAMBERS
A. A. COOK

J. I. CRABTREE

J. O. BAKER
T. C. BARROWS
P. E. CAHILL
J. R. CAMERON
A. A. COOK
J. K. ELDERKIN
J. J. FINN
R. R. FRENCH
E. R. GEIB

J. R. CAMERON
J. J. FINN

J. G. FRAYNE, Chairman
R. M. CORBIN
R. E. FARNHAM
H. C. HUMPHREY
W. LEAHY

PROGRESS AWARD

A. N. GOLDSMITH, Chairman
M. C. BATSEL

PROJECTION PRACTICE

H. RUBIN, Chairman
A. N. GOLDSMITH
A. GOODMAN
H. GRIFFIN
S. HARRIS
J. J. HOPKINS

C. F. HORSTMAN

D. E HYNDMAN
JOHN J. KOHLER
P. A. McGuiRE

PUBLICITY

W. WHITMORE, Chairman
S. HARRIS
G. E. MATTHEWS
W. A. MUELLER

G. E. MATTHEWS
V. E. MILLER
G. WORRALL

R. M. EVANS

E. R. MORIN

M. D. O'BRIEN

G. F. RACKETT

F. H. RICHARDSON

B. SCHLANGER

C. TUTTLE

J. S. WARD
V. A. WELMAN
A. T. WILLIAMS

P. A. McGuiRE
F. H. RICHARDSON

P. ARNOLD
M. C. BATSEL
F. C. BADGLEY
L. N. BUSCH
A. CHORINE
A. COTTET
L. DE FEO
A. C. DOWNES

J. A. DUBRAY

P. H. EVANS

W. C. KUNZMANN
J. H. KURLANDER

STANDARDS

E. K. CARVER, Chairman
R. E. FARNHAM
C. L. FARRAND
G. FRIEDL, JR.
H. GRIFFIN
A. C. HARDY
R. C. HUBBARD
E. HUSE
C. L. LOOTENS
K. F. MORGAN
T. NAGASE

STUDIO LIGHTING

R. E. FARNHAM, Chairman
V. E. MILLER
M. W. PALMER
G. F. RACKBTT

N. F. OAKLEY
G. F. RACKETT
W. B. RAYTON
C. N. REIFSTECK
H. RUBIN

0. SANDVIK
H. B. SANTEE
J. L. SPENCE

J. VAN BREUKELEN

1. D. WRATTEN

E. C. RICHARDSON

F. WALLER

338 COMMITTEES OF THE SOCIETY

SECTIONS OF THE SOCIETY
(Atlantic Coast)

G. FRIEDL, JR., Chairman

L. W. DAVEE, Past- Chairman M. C. BATSEL, Manager

D. E. HYNDMAN, Sec.-Treas. H. GRIFFIN, Manager

(Mid-West)

C. H. STONE, Chairman

R. F. MITCHELL, Past-Chairman O. B. DEPUE, Manager

S. A. LUKES, Sec.-Treas. B. E. STECHBART, Manager

(Pacific Coast)

K. F. MORGAN, Chairman

G. F. RACKETT, Past-Chairman J. O. AALBERG, Manager

G. A. CHAMBERS, Sec.-Treas. H. W. MOYSE, Manager

FALL, 1937, CONVENTION

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA, NEW YORK
OCTOBER llth-14th, INCLUSIVE

Officers and Committees in Charge

W. C. KUNZMANN, Convention Vice-President

J. I. CRABTREE, Editorial Vice-President

S. K. WOLF, President

O. M. GLUNT, Financial Vice-President

G. E. MATTHEWS, Chairman, Papers Committee

G. FRIEDL, Chairman, Atlantic Coast Section

Local Arrangements and Reception Committee

G. FRIEDL, JR., Chairman

O. M. GLUNT A. S. DICKINSON E. A. WILLIFORD

H/B. SANTEE M. C. BATSEL E. G. MINES

A. N. GOLDSMITH H. RUBIN V. B. SEASE

L. W. DAVEE J. FRANK, JR. D. E. HYNDMAN

E. I. SPONABLE O. F. NEU J. A. NORLING

Registration and Information

W. C. KUNZMANN, Chairman
E. R. GEIB S. HARRIS F. HOHMEISTER

Ladies' Reception Committee

MRS. S. K. WOLF and MRS. O. F. NEU, Hostesses
MRS. O. M. GLUNT MRS. T. E. SHEA MRS. A. S. DICKINSON

MRS. H. GRIFFIN MRS. J. FRANK, JR. MRS. E. A. WILLIFORD

MRS. E. I. SPONABLE MRS. G. FRIEDL, JR. MRS. M. C. BATSEL

Banquet Committee

A. S. DICKINSON, Chairman

O. M. GLUNT W. C. KUNZMANN H. GRIFFIN

J. H. SPRAY S. HARRIS O. F. NEU

G. FRIEDL, JR. M. C. BATSEL H. B. SANTEE

Publicity Committee

W. WHITMORE, Chairman

J. J. FINN G. E. MATTHEWS F. H. RICHARDSON

J. R. CAMERON S. HARRIS P. A. McGuiRE

339

340 FALL CONVENTION [J. S. M. P. E.

Projection Committee

H. GRIFFIN, Chairman

H. RUBIN F. E. CAHILL, JR. G. C. EDWARDS

J. O. BAKER M. D. O'BRIEN A. L. RAVEN

P. D. RIES J. S. WARD C. F. HORSTMAN

J. FRANK, JR. C. R. WOOD

Officers and Members of New York Projectionists Local 306, I. A. T. S. E.

Membership Committee

E. R. GEIB, Chairman

S. HARRIS A. A. COOK J. A. MILLER

J. A. HAMMOND J. K. ELDERKIN J. R. MANNHEIMER

Hotel Accommodations

O. F. NEU, Chairman

P. A. McGuiRE M. W. PALMER J. H. KURLANDER

D. E. HYNDMAN J. J. FINN P. D. RIES

Headquarters

The headquarters of the Convention will be the Pennsylvania Hotel, where ex-
cellent accommodations have been assured and a reception suite will be provided
for the Ladies' Committee. An excellent program of entertainment will be ar-
ranged by the hostesses.

Special hotel rates guaranteed to SMPE delegates, European plan, will be
as follows:

One person, room and bath $3 . 50

Two persons, double bed and bath 5.00

Two persons, twin beds and bath 6 . 00

Parlor suite, one person 11 .00 up

Parlor suite, two persons 13.00 up

Room reservation cards will be mailed to the membership of the Society in the
near future, and everyone who plans to attend the Convention should return his
card to the Hotel promptly in order to be assured of satisfactory accommodations.
Consult your local railroad ticket agent with regard to coach and pullman rates.

Parking accommodations will be available to those who motor to the Conven-
tion at the fire-proof garage of the Hotel, at the rate of $1 .25 for twenty-four hours
or $1.00 for twelve hours, including pick-up and delivery at the door of the Hotel;
weekly rate, $7.50.

Technical Sessions

An attractive program of technical papers and presentations is being arranged
by the Papers Committee. All technical sessions, apparatus symposiums, and
film programs will be held in the Salle Moderne of the Hotel, on the eighteenth
floor.

There will be no general Apparatus Exhibit, but those who have developed new
equipment during the past year are invited to submit technical descriptions of it
to the Papers Committee for possible inclusion in the Apparatus Symposium.

Sept., 1937] FALL CONVENTION 341

Registration

Registration headquarters will be located on the eighteenth floor of the Hotel at
the entrance of the Salle Moderne, where the technical sessions will be held. Ex-
press elevators from the lobby will be reserved for the Convention. All members
and guests attending the Convention are expected to register and receive their
badges and identification cards required for admission to certain evening sessions
of the Convention, as well as to various de luxe motion picture theaters that will
honor the cards as courtesy admissions.

Luncheon and Banquet

The usual informal get-together luncheon will be held at noon on October llth
in the Roof Garden of the Hotel, and the semi-annual banquet and dance will
take place on the evening of October 13th.

Addresses will be delivered by prominent members of the industry on both
occasions. At the banquet the annual presentation of the SMPE Progress Medal
and the Journal Award will be made, and the officers-elect for 1938 will be intro-
duced. The banquet will conclude with dancing and entertainment.

Tickets for admission to the informal luncheon and the banquet may be ob-
tained at the registration desk. Banquet tables reserved for 8, 10, and 12 per-
sons.

Ladies' Program

An especially attractive program for the ladies attending the Convention is
being arranged by Mrs. S. K. Wolf and Mrs. O. F. Neu, Hostesses, and the Ladies'
Committee.

A suite will be provided at the Hotel, where the ladies will register and meet for
the various events on their program. Further details will be published in a suc-
ceeding issue of the JOURNAL.

Entertainment and Diversion

Golfing privileges may be arranged at several country clubs in the vicinity of
New York, as well as various tours to points of interest in and about the city.
These arrangements may be made either at the Convention registration desk or
through the management of the Hotel.

Points of Interest

Headquarters and important branch offices of practically all the important firms
engaged in producing, processing, and exhibiting motion pictures and in manu-
facturing equipment therefor, are located in metropolitan New York. Although
no special trips or tours have been arranged to any of these plants, the Conven-
tion provides opportunity for delegates to visit those establishments to which they
have entree. Among the points of interest to the general sightseer in New York
may be listed the following :

Metropolitan Museum of Art. — Fifth Ave. at 82nd St.; open 10 A.M. to 5 P.M.
One of the finest museums in the world, embracing practically all the arts.

American Museum of Natural History.- — 72nd St. between Columbus Ave. and
Central Park West; 9 A.M. to 5 P.M.

342 FALL CONVENTION

New York Museum of Science and Industry. — RCA Building, Rockefeller Cen-
ter; 10 A.M. to 5 P.M. Exhibits illustrate the development of basic industries,
arranged in divisions under the headings food, industries, clothing, transportation,
communications, etc.

Museum of the American Indian. — Broadway and 155th St., 2 P.M. to 5 P.M.

Hayden Planetarium. —Central Park West at 77th St. Performances at 1 1 A.M.,
2 P.M., 3 P.M., 4 P.M., 8 P.M., and 9 P.M. Each presentation lasts about
45 minutes and is accompanied by a lecture on astronomy.

Rockefeller Center. — 49th to 51st Sts., between 5th and 6th Aves. A group of
buildings including Radio City Music Hall, the Center Theater, the RCA Building,
and the headquarters of the National Broadcasting Company, in addition to
other interesting general and architectural features.

Empire State Building. — The tallest building in the world, 102 stories or 1250
feet high. Fifth Ave. at 34th St. A visit to the tower at the top of the building
affords a magnificient view of the entire metropolitan area.

Central Park. — 59th to 110th Sts., Central Park West to Fifth Ave. Here are
located the Metropolitan Museum of Art, and a number of other general and
educational features including the zoological garden and "Cleopatra's Needle."
The latter is an Eyptian obelisk presented to the City in 1879 by the Khedive of
Egypt.

Greenwich Village. — New York's Bohemia; a study in contrasts. Here are
located artists and artisans, some of the finest homes and apartments, and some
of the poorest tenements.

Holland Tunnel. — The first vehicular tunnel constructed beneath the Hudson
River; at Canal St., connecting New York with New Jersey; more than 9000
feet long.

Foreign Districts. — Certain sections of the city are inhabited by large groups of
foreign-born peoples. There is the Spanish section, north of Central Park; the
Italian district near Greenwich Village; Harlem, practically a city in itself, num-
bering 300,000 negroes; Chinatown, in downtown Manhattan; the Ghetto, the
Jewish district; and several other such sections.

Miscellaneous.— Many other points of interest might be cited, but space permits
only mentioning their names. Directions for visiting these places may be obtained
at the Convention registration desk: Pennsylvania Station, Madison Square,
Union Square, City Hall, Aquarium and Bowling Green, Battery Park, Washing-
ton Square, Riverside Drive, Park Avenue, Fifth Avenue shopping district, Grand
Central Station, Bronx Zoo, St. Patrick's Cathedral, St. Paul's Chapel, Cathedral
of St. John the Divine, Trinity Church, Little Church Around the Corner, Wall
St. and the financial district, Museum of Natural History, Columbia University,
New York University, George Washington Bridge, Brooklyn Bridge, Triborough
Bridge, and Statue of Liberty.

Steamships. — The S. S. Normandie will be in dock open for inspection, on Octo-
ber 12th, pier 88 at the foot of West 48th St.: tickets on sale at the pier. 50tf each.

SOCIETY ANNOUNCEMENTS

1938 ELECTIONS

On or about September 1st, ballots will be mailed to the Fellows and Active
members of the Society for voting for Officers for 1938. The nominees are as
follows :

K. F. Morgan, Executive Vice-P resident

L. A. Jones, Engineering V ice-President

E. A. Williford, Financial Vice-President

J. Frank, Jr., Secretary

L. W. Davee, Treasurer

H. Griffin, Governor

A. S. Dickinson, Governor

A. C. Hardy, Governor

G. F. Rackett, Governor

W. A. Mueller, Governor

R. E. Farnham, Governor

Three of the six nominees for Governor are to be elected. The executive vice-
president, the secretary, and the treasurer are elected for one-year terms; the
other officers and governors for two-year terms.

The ballots will be counted on the opening day of the Fall Convention at New
York (October llth), and announcement of the results will be made immediately.
The officers-elect will be presented at the semi-annual banquet on October 13th,
and will assume office on January 1st.

The remaining officers and governors, named below, continue in office until
December 31, 1938:

S. K. Wolf, President

H. G. Tasker, Past-President

J. I. Crabtree, Editorial Vice-President

W. C. Kunzman, Convention Vice-President

M. C. Batsel, Governor

A. N. Goldsmith, Governor

KINEMATOGRAPH EXHIBITION OF THE ROYAL PHOTOGRAPHIC
SOCIETY OF GREAT BRITAIN

An exhibition of cinematography, comprising films, stills, and apparatus will be
held at the galleries of the Royal Photographic Society at 35 Russell Square,
London, W.C.I, November 13-27, 1937.

The keynote of the exhibition will be "The Film as a Social Force." During its
course, lectures and demonstrations of interest to both professionals and amateurs
will be given.

343

344

SOCIETY ANNOUNCEMENTS

[J. s. M. p. E.

A competition, embracing films of all types, has been arranged, the rules and
entry form for which may be obtained by writing to the secretary of the Society
at the above-given address. A selection from the films receiving awards will be
shown during the exhibition.

ADMISSIONS COMMITTEE

At a recent meeting of the Admissions Committee, at the General Office of the
Society, the following applicants for membership were admitted to the Associate
grade:

ALLISON, D. K.

Chemical & Research Corp.,
9308 Santa Monica Blvd.,
Beverly Hills, Calif.
BERNZOTT, H.
4151 N. Mozart St.,

Chicago, 111.
BRETHAUER, F. L., JR.
2125V2 Ridge Ave.,

Evanston, 111.
BRUESKA, G. A.
2216 Lunt Ave.,

Chicago, 111.
DEMMER, A. H.
Ill Chestnut St.,
Audubon, N. J.

DlSciULLO, H.

144 Westville St.,

Dorchester, Mass.
DOOLITTLE, J. N.
3426 W. Olympic Blvd.,

Los Angeles, Calif.
FERSTER, R.
3601 44th Ave., South
Minneapolis, Minn.
HALL, T. O.

Hall & Connolly, Inc.,
24 Van Dam St.,
New York, N. Y.

HOUSKEEPER, W. G.

512 Clark St.,

South Orange, N. J.
JUST, J. J., JR.
5329 School St.,

Chicago, 111.
KEMNA, G.
Neu-Babelsberg
Wilhelmstr. 9,
Berlin, Germany.

KNOESPLER, J. M.
1434 School St.,

Chicago, 111.
LEONARD, R. S.

Seattle Lighting Dept.,
City Light Bldg.,
Seattle, Wash.
LIPMAN, H. R.
308 W. 94th St.,

New York, N. Y.
LYMAN, T. B.
577 Floral Drive,
Whittier, Calif.
MACK, W.

4520 N. Damen Ave.,
Chicago, 111.

McCULLOUGH, J. D.

779 Simpson Ave.,

Salt Lake City, Utah.
NARAYANAN, P. L.

The Gramophone Co., Ltd.,
Post Box No. 118, Fort
Bombay, India.
PEEK, J. E.

708 W. Grand Ave.,
Oklahoma, Okla.
PENNIWELL, A. F.
2838 S. Gaffey St.,
San Pedro, Calif.
SARAZEN, E. P.
4411 Regent St.,
Duluth, Minn.
SCHULTZ, C. E.

Heyer-Schultz, Inc.,
39 Orange Road,
Montclair, N. J.
SONNENBERG", A. C.
3130 S. Karlov Ave.,
Chicago, 111.

Sept., 1937]

SOCIETY ANNOUNCEMENTS

345

STAPLEFELD, O.

1584 W. Washington Blvd.,

Los Angeles, Calif.
STERN, B.

467 Central Park West,

New York, N. Y.
STRAUSS, E. E.

329 Washington Ave.,

Wilmette, 111.
STRYKER, G. E.

4254 N. Mozart St.,
Chicago, 111.

TUPPER, J. A.

2319 Doughlass St.,

Brooklyn, N. Y.
TUSLA, L.

68, Kensington Mansions,
Earls Court, London, S.W. 5.
England.

WILSON, H. A. McG.
Cummings & Wilson,
29 Alberta St.,
Sydney, Australia.

In addition, the following applicants have been admitted by vote of the Board
of Governors to the Active grade:

HARRIS, W. M.

7063 Lancewood Ave.,

Hollywood, Calif.
POTURN, C. C.
815 Riverside Drive,
New York, N. Y.
SKLAR, S. B.
27 W. 72d St.,
New York, N. Y.

STONG, C. L.

Electrical Research
Products, Inc.,
250 W. 57th St.,
New York, N. Y.

WOLSKY, M.

117 Beach 59th St.,
Arverne, L. I.

Cameramen on loca-
tion in the desert near
Yuma, Arizona, are
working under diffi-
culties in shooting
this scene from the
Technicolor produc-
tion, "The Garden of
Allah." Marlene Dietrich and
CharlesBoyer co-star in this David
O. Selznick production, under the
direction of Richard Boleslawski.
IlowardCreene,Photographer;Hal
Rosson, Photographic adviser; W.
A. Oettel, Studio Chief Electrician

Exceptional penetration and carrying power are required of
light source to pierce the obscuring clouds of a sand stoi
on the desert, but the carbon arc proved equal to the task

__

> required of a H
a sand storm H

I tr> the task. iH

• It is silenf, cool ond remarkably fait.

• It has the photographic qualities of daylight.

• It has proved a necessity for color productions

• It Improves black and white photography.

HIGH INTENSITY CARBONS
MOTION PICTURE STUDIO CARBONS

NATIONAL CARBON COMPANY, INC,

Umt of Union CarkiJ» (TJlj^ and Carbon Corpo.ation
CARBON SALES DIVISION. CLEVELAND, OHIO

GENERAL OFFICES: 30 EAST 42ND STREET, NEW YORK, N Y.
RANCH SALES OFFICES. NEW YORK . _ P1TTS6URBH . CHICAGO . SAN f RANC

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX OCTOBER, 1937 Number 4

CONTENTS

Page

How Motion Pictures Are Made — A Symposium of the Spring,

1937, Convention, Held at the Universal Studios 349

Preparing a Story for Production ROBERT PRESNELL 350

Prescoring for Song Sequences BERNARD BROWN 356

Set Design from Script to Stage JOHN HARKRIDER 358

Handling Lighting Equipment in Production . FRANK GRAVES 360

Film Editing MAURICE PIVAR 363

Setting Music to Pictures CHARLES PREVIN 372

Assembling a Final Sound-Track EDWIN WETZEL 374

Report of the Sub-Committee on Perforation Standards 376

A New Dynamic Light- Valve E. GERLACH 388

Color Stills O. O. CECCARINI 397

Mathematical Relations between Grain, Background Noise, and

Characteristic Curve of Sound-Film Emulsions

W. J. ALBERSHEIM 417

New Motion Picture Apparatus:

Laboratory Equipment for the Smaller Laboratory

A. REEVES 446

Current Literature 455

Fall Convention : Hotel Pennsylvania, New York, N. Y., Octo-
ber 11-14, 1937

General Information 457

Tentative Program 461

Society Announcements 466

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS, EDITOR

Board of Editors
J. I. CRABTREE, Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum; to members, $5.00 per annum,
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y.
Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers in question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 100 E. 42nd St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 180 Varick St., New York, N. Y.
Convention V ice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK, JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York, N. Y.

GOVERNORS

M. C. BATSEL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 25 Hunter Ave., Fanwood, N. J.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE, 205 W. Wacker Drive, Chicago, 111.-

HOW MOTION PICTURES ARE MADE

SPECIAL EVENING DEMONSTRATION AT

THE STUDIOS OF UNIVERSAL PICTURES CORPORATION

MAY 25, 1937

As one of the events of the Spring, 1937, Convention of the Society held at Holly-
wood, Calif., a symposium on the subject of "How Motion Pictures Are Made" was
arranged by members of the staff of Universal Studios, Mr. H. G. Tasker* acting
as Chairman. The audience of members and guests of the Society, numbering in
excess of 600 persons, assembled at 8 P.M. on stage 10 of the Studio, which is normally
devoted to scoring and prescoring.

MR. H. G. TASKER :* Ladies and gentlemen, I am sorry to announce
that Mr. Chas. R. Rogers, Executive Producer and Vice- President of
Universal Pictures, is unable to be here tonight to welcome you as he
had planned to do. We are most fortunate, however, that he has
sent, to represent him, not only a most able assistant, but also a man
whom we at Universal regard most highly. I am happy to introduce
to you our Studio Manager, Mr. Val Paul.

MR. VAL PAUL : It is hardly necessary to make a speech of wel-
come, because I want every member of your Society to feel at any
time that you are here, and particularly at this time, that the gates
and doors of Universal City are always open to you. I hope you
will take advantage of that so that we may serve as your host at any
time the Society may happen to meet in our fair city.

Nevertheless, I deem it a pleasure to speak before you, whom I
might term the unsung heroes of the motion picture industry. I say
that because I feel that most of you gentlemen who are connected
with the Society are never seen or never heard; yet through your
efforts you have made it possible for millions to see and hear their
favorites on the screen.

I thank you all for coming here, and I certainly hope that you will
enjoy the program that the boys have prepared for you.

MR. TASKER : We have an interesting program for you this even-
ing, one by which we hope to aid in a very small but perhaps impor-

*Chief Sound Engineer, Universal Pictures Corp., Universal City, Calif.

349

350

How MOTION PICTURES ARE MADE [J. S. M. P. E.

tant way the men who are working in the industry, by giving you a
little more intimate view into the way motion pictures are produced
than is ordinarily available. Sometimes even those of us who are
immersed in studio work do not have a very good chance to see how

Left to right: (Standing) Edwin Wetzel, Dubbing Mixer; Charles Previn.
Musical Director; (seated) Maurice Pivar, Supervising Editor; Bernard
Brown, Chief Mixer; Homer Tasker, Sound Director.

our colleagues in the other departments work, and I confess that I have
been looking forward to this evening with some pleasure in the hope
of learning from Mr. Presnell and Mr. Harkrider and Mr. Graves,
and from each of the other men on the program tonight, some things
about the way their work is done of which I had no inkling before.
The first of our speakers this evening is a man who is responsible
for getting a picture started and for carrying it through to a success-
ful conclusion; upon whose shoulders rests the responsibility of pro-
duction. I am happy to introduce Mr. Robert Presnell, associate
producer at Universal.

PREPARING A STORY FOR PRODUCTION

ROBERT PRESNELL*

There is an old saying among us in the motion picture industry
that every picture is grief and that is the way it starts.

*Associate Producer, Universal Pictures Corp., Universal City, Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 351

When you see a picture in the theater and it rolls out smoothly in
front of your eyes you probably have no idea of what has gone into the
making of that picture before it arrives in the hands of you engineers
and technicians, so we shall start at the beginning.

Assume that a story is purchased. How it is purchased is another
story of grief, but it does not enter into this picture. Together with
a number of other stories it is sent around to the producers on the lot,
who read the stories. Here is what they have to think about when
they read those stories:

Suppose you have to make four of the lower-budget pictures, and
you know that each of them is to cost the nominal sum of $125,000 to
$150,000, and no more. You must not exceed that, because that is
all you will get. The first problem that comes up when you read one
of the stories is, can it be made for that amount of money ? Of course,
you may have to take out this bit of story; put something there
that is a little different; or down there something that we have in
stock; but that will be all right. Suppose you decide that perhaps
the story is all right as far as the number and cost of sets are con-
cerned, so you will seriously consider producing it.

Now, the next thing is to find out whom you can get to play the
leading part. All right; there are Joe Dokes and Henry Smith and
Bill Brown ; but Joe Dokes costs you $25,000 a picture, so you can
not use him. Bill Brown costs $20,000, and there is a big accumula-
tion* on Henry Smith. You would like to use him, but the big ac-
cumulation, say, $15,000, would have to be taken up, so you can not
use him. Finally you simmer it down to some personality on the
lot, some young fellow who is just starting out. Perhaps he needs a
chance to do bigger things. He fits into the part and you know that
you can get him for $5000 for this picture and then perhaps you
will try to see whether you can make a star of him. So after fooling
about a bit you finally decide to use him.

Then you realize that because your final picture has to cost less
money than other types of pictures you have no well known personality
in it, and that, as a result, you have a box-office handicap.

That is not true of the higher-budget pictures, because there you
start out with your stars already cut out for you — the big names, and

"This is the amount of salary of a player who is on contract that has been paid
to him since his last picture and which is usually charged to the cost of his next
picture.

352 How MOTION PICTURES ARE MADE [j. S. M. P. E.

then you can "go to town." It is no problem then; it is the little
pictures that are difficult.

Having no box-office appeal in the personalities because you are
taking young, new actors not very well known, and are going to
try to make stars of them, what have you got to sell? You have to
sell the story angle, something that is fresh and new, presented in a
fresh way, that will attract people to the picture and make them like
it; something that is catchy and has something in it that will move
along, and that they will enjoy. That is the first thing you must
plan to sell as you read the story.

Next you have to decide upon the story strength itself, what its
situations are, how strong it is, and how logical. Finally you do de-
cide that it will make a pretty good story, but you realize that you
will have to change this and that, and instead of the man biting the
girl, the girl will have to bite the man, and so forth and so on. Finally
you drop a note to Mr. Rogers, telling him that you would like to
try this story, that you see a fresh angle in it, and think that you can
do it within the money allowance. Perhaps the next morning you
find a note on your desk, telling you that it is "in your lap," and you
have got it.

The next thing you do is to call in the scenario head. You need
a writer to start putting the story into producible form. Now we
are in a new phase of the production. You have already had a few
headaches to start with, but here are some new ones. You want a
writer, and look through the list of available writers in Hollywood.

Now, as in any other business, the good writers are all pretty well
tied up in other places when you want them. You have to find some-
body who you know can write that story the way you want it, and
who does not get more money than you feel you can allow. Writers
get all the way from $150 to $3500 or $4000 a week. I have always
said that it is better economy to use a good writer, no matter what
you have to pay, and use him for less time, than it is to use a poor
writer and spread the work over many, many weeks, because you
will always get into trouble by doing so.

So you go through the list of available writers. There are not too
many writers here in Hollywood — not as many as you think. There
are probably about four or five hundred writers doing business in
Hollywood, and about 100 of them, or less, do all the actual work; so
out of the 85 or 100 you have to pick one who can do the story within
all the limitations that are beginning to hedge about you. Finally

Oct., 1937] How MOTION PICTURES ARE MADE 353

you decide upon Willie Smith. He is a good writer, so you engage
him. You talk to him, and tell him the story, and let him read it.
He comes in the next day; perhaps he is enthusiastic about the pic-
ture. He has a new angle on it, which he wants to try. You give
him the job, and he starts to work. You tell him further that this is
a picture that has to be done, let us say, in 18 shooting days. You
have to shoot it within 18 days because it is costing you from $3000
to $5000 a day to shoot the picture, so if you run over that you will
run over your budget; furthermore, if you are going to shoot the
picture in 18 days, you should not have more than 18 sets in the pic-
ture. You do not want a lot of costly moving about, but what you
do want is to be able to shoot in any one set for a full day at least. It
is much more economical to do it that way. So the writer starts to
write the picture, keeping in mind the charges and keeping the sets
down to a minimum.

In this kind of picture, we always try to say something. It must
be about something. Most of the pictures have headlines, things
that sell themselves; things of general interest, which carry the in-
terest as the story is told through the characteristics of people who
move and breathe and do things.

Finally, in a picture of this kind, after about four or five weeks,
you get your first draft. The first draft is your springboard, as we
say in the motion picture industry, out of which your story is built.

Now you have got something tangible in your hand, and can weigh
it. It should be about 100 or 105 pages long in order to get about
6000 feet of finished film, which is what you want; you know exactly
the number of sets required, and in order not to run over the schedule
you want to be sure that there are no sets in the script that cannot be
produced in the length of time set.

With the first draft, you go into the first conference with your
writer and the head of your story board — if you have one — and in this
case we usually go to Mr. Val Paul. He reads the story and says
it is wrong here or it is wrong there ; and so with the writer and Mr.
Paul you straighten out all the questionable points, cut out all the
dead spots, and so forth, so that the story moves quickly, rapidly,
and amusingly, right straight through. You cut out all the long
walks down hallways and things of that sort; you seem to jump from
one scene into another scene so that the whole moves right along,
each scene building higher and higher as the story progresses.

After the conference you are ready for your second draft, and then

354 How MOTION PICTURES ARE MADE [J. S. M. P. E.

you call in your director to read the story. The director wants some
changes; he has certain problems to bring up; he wonders whether
or not this scene can be done; something has to be done here, and
something has to be done there; so a little more of the grief comes in
with the director, who also adds to the cost of the picture. You
have to engage a director who will not cost too much, or there
will be an over-balance again. You have to maintain your balance
all the way through.

Finally the director has had his say, and an assistant director is
assigned to him and a cutter is put on the picture. You go into the
final draft, making all the changes agreed upon, and finally get out
the final draft, and it is satisfactory. Before that happens, how-
ever, the first draft goes to Mr. Murphy, head of the production
department, who sometimes holds it up and sometimes says it is
all right.

Production department problems are a little different. The
script is read and estimating begins. Every scene in the script must
be estimated, how many persons are in it, what it will cost to build
each set, what the wardrobe will cost, what the lighting will cost, and
what the sound will cost. Everything that goes into the cost of a
scene is figured, and the sum of all the estimates for each scene con-
stitutes your budget. Sometimes the estimate is high, and some-
times it is very close to your aim; but sometimes you find it impos-
sible to do the picture with the money allowed, and then you have to
do some re-vamping, some more cutting down and changing to bring
the cost within your limits. Finally you get it within those limits,
and then the art department goes to work. Blueprints are made of
the sets and so forth — Mr. Harkrider will tell you what is done in
that department. You choose a title for the picture, and then you
are almost ready to start. Your director and assistant director are
ready, and the cameraman and the whole crew have been assigned
and are "ready to go."

Now comes the casting. The casting director and associate
producer sit down to argue the problem ; and when four or five per-
sons in a room are asked their opinions of something, you may ex-
pect to get four or five different opinions. That usually happens in
the casting, at least, for the smaller parts. The big parts are pretty
well settled, as you have had them in mind from the very beginning.
As to the smaller parts, you talk it over and you find out whether
this one or that one will do ; then you have to find out whether they

Oct., 1937] How MOTION PICTURES ARE MADE 355

are available, whether they are under contract either to you or to
another studio, or whether they are busy at another picture
elsewhere. If they are busy, you have to get some one else. If you do
borrow an actor from another studio you pay somewhat more
than you do for your own people. You have to pay what is called
the "three-and-f our- weeks," that is, pay four weeks' salary for three
weeks' work. All this affects your budget, and again you have to
find actors who are adequate to play the parts at prices within your
range, and you have to reach out and get them wherever you can in
the industry. Sometimes it is very difficult, and sometimes you have
to juggle your schedules so that the work will continue right through
without your having to carry the actors along for too long a time.
There is a rule in Hollywood that if you start with a character in a
picture — if he has started, say, on the second day of the picture, and
his next scene does not come until the sixteenth day of the picture,
you have to pay him from the second day right through to the six-
teenth. It used to be in the old days that you might be able to make
a deal with him and pay him for the two days' work; but not any-
more. . For that reason the schedules have to be rearranged in such
a way that all actors (except your own contract players) run through
their scenes almost consecutively. Sometimes it is necessary to
carry actors for a day or two, but if it is more than that, it runs into
a lot of money.

Finally the casting is done ; you sit down with a sigh of relief, and
your picture is ready to start the next morning. When the fateful
morning comes, you go down to your first set, shake everybody's hand,
and then get off the set very quickly. Now your grief really begins.

MR. TASKER : Although Mr. Presnell has taken us from the point
of choosing the story material clear up to the start of production,
there are two steps that we shall discuss further this evening. One
of these, already mentioned, is the work of the art department, which
will be described in a few minutes. The other occurs whenever there
are to be songs or musical numbers in a picture, and since it comprises
making some of the music for the picture before any shooting begins,
it is called "prescoring." Mr. Bernard Brown, the head of our music
and effects department, will describe and demonstrate prescoring
for sound sequences.

356 How MOTION PICTURES ARE MADE [J. S. M. P. E.

PRESCORING FOR SONG SEQUENCES

BERNARD BROWN*

As most of you know, we do not record songs or orchestras on the
set during the filming of a picture. Instead, we record them in ad-
vance, usually before the picture goes into production. This we
call prescoring. We prescore for several reasons, which I shall ex-
plain as I outline the method of prescoring.

To record a vocal selection with orchestral accompaniment we
bring the soloist and the orchestra to this stage, which has been built
for music recording. We are able to do much better musical record-
ing here than on the sound stages, partly because we can use micro-
phones close to the different sections of the orchestra. That could
not be done if the orchestra were photographed at the time of record-
ing because the microphones would show in the picture.

First, we rehearse the orchestra alone, to check the arrangement
and to see that there are no mistakes in the music Then, the soloist
rehearses with the orchestra, showing the musical director and the
orchestra exactly how she would like the accompaniment played.

Next we record the orchestra alone, the soloist mouthing the words
silently and the musical director following her and directing the
orchestra accordingly. If this is a good "take" the orchestra is dis-
missed.

This procedure is very economical, as we finish with the musicians
in one-half the time that used to be required to record both voice
and orchestra at the same time, making take after take and finally
being forced to use one of the last takes made when the soloist was
tired.

Now we have an ideal set-up for the soloist. The orchestra has
gone, and no one is allowed upon the stage who is not actually working
on the recording.

Next we play back the orchestral record we have just made, us-
ing head-phones to listen to it.

As you notice, the soloist has only one earphone, so that she is able
to hear the music played back with one ear and her own voice with
the other. The music is played at a fairly low level so that our soloist
can hear clearly every note she sings without its being covered by
the orchestra. In order to pronounce her words clearly and get the

* Chief Music and Dubbing Mixer, Universal Pictures Corp., Universal City
Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 357

proper tone placement in her throat it is sometimes necessary for
the singer to make peculiar faces, which she can do without em-
barrassment as she is among friends and is not being photographed.
In recording the songs it is not necessary to make many takes,
as we are able to take the best parts of two or three takes and assem-
ble them into one good take, which saves a lot of time in addition to
the soloist's voice. When this assembly has been done, we make a
combined record of voice and orchestra which we use as a playback
on the set when photographing the scene in which the soloist is sup-
posed to sing the song. Photographing a scene with playback is done
as follows : The record of the song is placed upon a reproducing ma-
chine which is interlocked with the camera so that the camera and
the playback run at the same speed. As the camera turns and photo-
graphs the actor, the record is reproduced over a loud speaker and
the singer mouths the words of the song again, either silently or other-
wise, without having to make the excessive facial contortions re-
quired for tone placement and enunciation. Here is where the pre-
scoring is very helpful to the singer, because she can now think about
the scene and look her best, without having to worry about the qual-
ity of her singing.

At the conclusion of Mr. Brown's paper, Miss Deanna Durbin was introduced to
the audience and sang" Sunbeams" from the Universal Picture "One Hundred Men and
a Girl," then in production. Head-phones had been wired throughout the audience so
that the spectators could listen to the orchestral playback as Miss Durbin sang her song
for the recording.

This prescored recording was later to be dubbed into the picture photographed on
the production stage as described below.

MR. TASKER: Although designing the sets for a motion picture
begins as soon as, if not sooner than, the prescoring, we prefer to
make it follow the prescoring on this program in order to show
the logical unfolding of a set creation from script to stage. In illus-
tration of this subject the art deparment will present drawings and
models of the very set in which later portions of this evening's pro-
gram will take place. Through the courtesy of Mr. John Harkrider,
supervising art director at Universal, the next paper will be pre-
sented by Mr. Michael Fitzmaurice, whom you have no doubt seen
in a number of Universal pictures.

358 How MOTION PICTURES ARE MADE [J. S. M. P. E.

SET DESIGN FROM SCRIPT TO STAGE

JOHN HARKRIDER*

It is my purpose this evening to paint a word picture of New Uni-
versal's art department; to show you how it works and functions;
to give you, somehow, the feeling that pulsates through the members
of its entire staff.

First, I usher you into a long, low, white building. Youth and
activity sound the keynote of the outer office — the apprentice room.

Herein is a story : We of the New Universal art department sin-
cerely believe in the ambition and creative ability of youth, yet real-
ize that every youth lacks experience and form. We give them the
chance to acquire experience and form, by selecting a number of
promising young men and training them, and giving them construc-
tive criticism individually. Later, if they show the proper develop-
ment, and many of them do, they are given positions on the staff.
The talent so discovered and to be discovered is inestimable.

We pass into the inner office where the art director and his asso-
ciates work. To give you an idea of their work I shall explain how
the department functions from the time it receives a script to the
time a set is struck.

The scenario department turns the script over to the art depart-
ment. The art director and his associates carefully study it to de-
termine the types of sets that are to be used. The artists then be-
gin to prepare sketches keyed to the particular plot and mood of the
story. Each scene must be visualized in its entirety. The sketch
artists must be very versatile, and must be able to design anything from
a small object, like a mantle piece, to a complete set. His sketches
must show both the artistic and the mechanical side of the set. After
the various designs are finished the art director chooses the best one
or two or incorporates the best features of several sketches into one
he thinks suitable.

The art director then holds conferences with the producer, the
director of the picture, and all the others involved, and details of
the picture are established.

The sketch that has been chosen is then turned over to the drafts-
man, who works directly from the sketch. The draftsman tells the
unit man the stock units incorporated in the set. If possible, the

* Supervising Art Director, Universal Pictures Corp., Universal City, Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 359

sketches include material and old sets already on the lot, which is a
great help economically. Their use is never noticed, and the beauty
or artistic value of the new set is never sacrificed. The unit man
checks the stock units, and then the draftsman prepares the plan.

After the plan is prepared a blueprint is made, which is sent to the
estimator for a prelimary estimate. The positive print is made for a
brown line print. This brown line print is sent to the creative plan
model department. The creative plan model department is of ex-
treme value from both an artistic and pecuniary standpoint.

A model of the set is prepared, which, when finished, is taken to a
conference of the producer, the director, the art director, and others.
It is at this meeting that the true value of these models is brought
out. The director can plot angles on them and plan the action.
Electricians can figure their lighting problems. Everyone concerned
can visualize the problems confronting him, and the models result
in a great saving in the cost of building useless sets. Every problem
is presented clearly.

When the model has been accepted final blueprints are made of
the set, which are submitted to the technical department. Con-
struction of the set then begins. A unit man is present to see that
the specifications of the plans are followed. Skilled carpenters and
technicians work on the sets. If anything is added to the set during
the construction the unit man takes care of all the details.

When the set is constructed it is turned over to the property de-
partment. The set is dressed by a set dresser, and the unit man sees
that the art department's plans are carried out. This is a very com-
plicated job, and everything must be placed correctly. Anything
amiss would ruin the effect as a composite picture.

The set is prepared and dressed twenty-four hours before shooting
time. The art director approves the set and then shows it to the
director, the cameraman, and others involved.

The art department also designs the costumes and appurtenances
worn by the players in the picture. It also works in close collabora-
tion with the wardrobe department to see that their ideas are com-
pletely carried out. The costumes are designed to harmonize with
the sets. They are also correct as to period and seem part of the
picture. These correct costumes also help the players psychologically
for they feel at home in the correct attire and atmosphere.

A set is always built using all the natural colors involved in the
real scene whether it be Technicolor film or not, the first and most

360 How MOTION PICTURES ARE MADE [J. S. M. P. E.

important reason being that the colors impart the correct atmosphere
from the aesthetic, logical, and psychological standpoints. Second,
the highly sensitized film of today picks up the true values of the
colors.

The art department maintains its own research organization,
the function of which is primarily to provide material for the sketch-
artists to help them with their ideas and to insure the authenticity
of their drawings. The researcher must be generally familiar with
practically all subjects, such as the periods of interiors, exteriors,
furniture, costumes, fashions, and so forth, so that when a call comes
for a modern Georgian interior, for example, the research department
will know immediately where to find it with the least possible delay.
Such subjects as animals, paintings, costumes, details, fashions, in-
teriors, exteriors, flowers, transportation, etc., are systematically
indexed, so that even the matter of finding material in current and
back issues of magazines can be accomplished with comparatively
little loss of time.

During the presentation of Mr. Harkrider's paper, Mr. Jack Smith, with easel,
paper, and crayon, demonstrated the manner of preparing the sketch of a set. At
the same time, Mr. Addison Hare, also of the Universal art department, indicated
the manner of preparing the corresponding plans of the set. A model of the set was
displayed, taken apart, and put together again by Mr. Paolo Grieco.

Following the proceedings thus far described, the members and guests of the Society
adjourned to Universal 's production stage 14, where they were shown the very set
from "Cm Hundred Men and a Girl" that has been described above. The set was com-
pletely dressed and lighted in the usual way with all the necessary equipment, and
was attended by a complete personnel for shooting the scene. Miss Deanna Durbin
and Mr. Mischa Auer, actors in the scene, were present and ready to go through
their parts. The scene was to be photographed while Miss Durbin played her part
singing the song that had already been prescored.

MR. TASKER: We shall now go ahead with the next part of our
program. Mr. Frank Graves, superintendent of the electrical de-
partment, will discuss the production part of handling the equipment
and how it works.

HANDLING LIGHTING EQUIPMENT IN PRODUCTION

FRANK GRAVES*

The function of "setting up" a set with lighting equipment does
not by any stretch of the imagination come under the heading of

* Superintendent, Electrical Department, Universal Pictures Corp., Universal
City, Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 361

artistic endeavor. It consists mainly in placing an abundance of
assorted kinds of equipment in suitable locations around and about
the set, so that when the cameraman is called upon to light a series
of camera set-ups, each of which is a separate problem, he has close
at hand and, as nearly as it is possible for him to foretell, the kinds of
lamps required in the proper places to light the particular shot.

Sets could be arranged with much less equipment than it is the
general practice to use, but the saving of time accomplished by not
having to move lamps about on the platforms more than compensates
for the cost of using the additional equipment.

Very seldom, except when making extremely long shots on very
large sets, are all the lamps on the set used for any one shot. As an
example, a set that was shot a few days ago had a connected load
of approximately 4000 amperes. Meter readings showed that the
largest operating load was 2100 amperes and the average about 900
amperes. The difference between the connected or "paper" load,
as we call it, and the operating load is allowed for in our calculations,
and we have often carried, on generators having a capacity of 18,000
amperes, a "paper" load of 50,000 to 60,000 amperes, without trouble
or worry.

A large part of the labor of arranging a set is in the cabling, since
it is necessary, of course, that all the lamps be fed and controlled.
The usual practice is to run main feeders from a spider or bus attached
to the runs from the power house, bring these main feeders to con-
veniently located switchboards, and from there, distribute the power
through extension cables and plugging boxes to various places on the
set.

At this studio we have eliminated a great portion of the labor
necessary to cable a set by installing a permanent remote-control
switchboard and cable system. On the platform above the set are
cabinets containing sixteen magnetic contactors connected to
the supply feeders from the power-house and controlled by push-
buttons. To each contactor are connected four box cables, sixty-
four cables in all. These box cables are spread over the bridges so
that they cover the entire stage. When cabling a set, it is necessary
for us only to drop the boxes, which are coiled on posts on the bridges,
let down the buttons that control the contactors to which these cables
are attached, plug in the lamps — and we are ready to shoot. All
stages at Universal are so equipped, and the problem of cabling a
set is, to us, a very minor one.

362 How MOTION PICTURES ARE MADE [J. S. M. P. E.

Now just a word about the "gaffer." The gaffer is the electrical
department's representative on the set, and is the man in full charge
of all electricians and equipment used by the unit to which he is as-
signed. He must be a combination of lighting expert, electrician,
economist, and psychologist. He must manage his unit with a mini-
mum number of men and in such a way that we do not exceed our
budget. He must be able to keep his unit operating on locations,
despite breakdowns of equipment or other unforeseen problems. He
must know all the tricks and moods of his cameraman so that he can
anticipate every wish. And last, he must watch the general light-
ing of the set and keep it right, despite the constant moving and
shifting of lights, so that the cameraman may concentrate upon the
finer details of his art.

MR. TASKER : According to the program there should now follow a
discussion of "Lighting for Long Shots and Close-Ups" by Mr. Val-
entine, cinematographer; "Sound Pick-Up on a Production Basis,"
by Joseph Lapis, Production Mixer, and "The Director's Problem,"
by Henry Koster, Director. This discussion will not be in a form of
a series of papers, but rather a running demonstration of the manner
in which an actual scene is made. Mr. Valentine and his assistant
will attend to the lighting. Mr. Lapis and his assistants will attend
to the sound equipment, and Mr. Joseph Pasternak, associate pro-
ducer on the picture One Hundred Men and a Girl, will pinch-hit for
Mr. Henry Koster, who, unfortunately, is too ill to be present this
evening.

In addition to these gentlemen, I am happy to present to you our
cast for the scene — Miss Deanna Durbin, whom you have already
seen earlier this evening, and Mr. Mischa Auer, whose amusing an-
tics have entertained you in previous pictures. In this scene, Mischa,
who is a life-long friend of Deanna's father, both of them being unem-
ployed musicians, is seated at the piano playing an accompaniment
to Deanna's song Sunbeams. This is the same song that you heard her
prescore a few minutes ago. We shall use the disk record that was
made at that time for Deanna to sing to in just the manner described
by Mr. Brown.

After Mr. Tasker's introduction, the camera, sound, and lighting crews went about
the business of making a long shot of Miss Durbin singing "Sunbeams" with Mischa
Auer at the piano, under the direction of Mr. Pasternak. As they went about their
work they explained many points concerning the technic and the reasons for it, and

Oct., 1937] How MOTION PICTURES ARE MADE 363

answered a number of questions from the audience. ' After the long shot a new set-up
was made for a close-up of Miss Durbin, repeating a portion of the song. The dif-
ference in lighting technic, sound pick-up, etc., were explained.

At the conclusion of the demonstration the audience reconvened upon stage 10
where the scenes made during the foregoing demonstration were projected. They were
first shown in the form of "dailies," take by take, exactly as photographed,
showing the slates identifying the scene numbers and other information. The cut
sequence was then projected, 'from which the slates had been removed and into which
several takes had been intercut into a continuous scene, as would appear in the finished
picture.

(It is hardly necessary to state, of course, that the finished scene, as projected, was
not the actual one shot during this evening's session; such would have been impossible
in view of the time required for processing, etc.).

MR. TASKER : It must be evident by now that the mere taking of
a scene on the stage does not constitute a completed picture, but
that there is a tremendous amount of finishing work that must be
done before the picture is ready to be shown in the theater. What
happens next is the function of the editorial department. Mr.
Maurice Pivar, supervising editor of Universal Pictures, will dis-
cuss the subject of film editing, followed by a demonstration of some
of the work.

FILM EDITING

MAURICE PIVAR*

Film editing is perhaps one of the few branches of the motion pic-
ture industry that are least appreciated by the layman. The efforts
of the director, the writer, the actor, and the cameraman are clearly
defined upon the screen, and the layman is at all times fully aware
and, in fact, appreciative of their contributions toward the success
or failure of the picture. True, the film editor's name always appears
upon the screen, but very few persons know of the intricacies in-
volved in his share of the work in making the picture. To them he is,
perhaps, just another cog in the wheel. On the other hand, those
who have had occasion to contact with the editorial department of
any studio will admit that the film editor is more than merely a
cog in the wheel.

Unlike most of the technical branches of the business, film editing
does not follow any particular routine. Each picture and each se-
quence of a picture present a different problem to the film editor,

*Supervising Editor, Universal Pictures Corp., Universal City, Calif.

364 How MOTION PICTURES ARE MADE [J; S. M. P. E.

especially so today, when the situations are tied up and involved
with sound elements.

The average successful editor must apply not only intelligence but
ingenuity to his work. He must not only know the mechanical
routine of editing but he must thoroughly understand and appreciate
screen values — whether they be dramatic, photographic, or other-
wise, and must take full advantage of the film he has in hand so that
it will play up to the audience to the best advantage.

In other words, a proficient editor must be one who feels dramatic
and comic impulses to the extent that he may convey these expres-
sions to the screen to the best advantage. An editor of a picture who
is devoid of this instinct would be of very little assistance to the
average director, even though he may be fully versed in the general
mechanics of editing.

Those who are familiar with production are aware that the average
feature picture involves approximately thirty thousand to sometimes
three hundred thousand feet of film, and it requires efficiency and
system for an editor to be able to place his hands upon any particular
scene at any time, without having to wade through thousands and
thousands of feet of film. The systems used for keeping track of
this excess film vary in the different studios. At this studio we have
systematized this phase of cutting through the cooperation of our
laboratory and production departments. After each day's work
on the set, the script girl sends to the editor a copy of her record of
the day's work. This record records clearly the number, length,
and dialog of each scene, and is kept on file from day to day by the
editor. Time and again during the course of editing a picture, a
director will wish to change a scene from one angle to another; and
sometimes there is a question as to whether such a scene may have
been shot, or whether such a scene was complete — and to avoid wad-
ing through the film to find the answer, the editor instead refers to
the script girl's notes.

In addition to the script girl's records, a laboratory record is also
kept by each editor. This record is sent through with the film printed
up each day by the laboratory (commonly termed "dailies").
The edge numbers and scene numbers of each scene printed are
marked upon this record. These records are used for reference con-
tinually while the picture is in the process of editing, particularly
when reprints of certain scenes are required. '

Through the medium of these records, the editor is enabled, by

Oct., 1937] How MOTION PICTURES ARE MADE 365

checking the edge number on the film with the edge number on the
record, to find the scene number of the particular scene required to
be reprinted. Quite often during the editing of a picture, a scene
is either damaged or, more often, cut up by the changing of cuts, to
the extent that a reprint is necessary for practical handling. The
laboratory records and the script girl's daily records facilitate order-
ing these reprints and checking the various scenes of the picture.

As we all know, in cutting a sequence a number of trims are left
over from each scene. These trims, likewise, are kept in orderly
fashion. The trims of each sequence are kept intact and labelled,
then placed away with the name or number of the sequence. In this
way, the editor, should occasion arise, can find the trims of any scene
by looking through the trims of the sequence involved. If there
should be fifteen sequences in a picture, the editor would have fifteen
separate files of trims on hand in his cutting room.

The mechanical routine involved in the preliminaries of editing a
picture also vary somewhat in the different studios. The majority,
however, favor the use of separate sound-track and separate action
films during the process of editing. Several studios, however, use
movietone prints — prints that have the sound already printed on the
film with the action. This method may be more economical from
the standpoint of saving film, but I prefer the separate sound-track
for the reason that it offers greater latitude in editing and makes the
process of cutting more flexible.

The first step in connection with editing, as a rule, is to synchronize
the sound-track with the action. This is accomplished by the use of
a mark or punch at the beginning of each scene. The punch or mark
is made on both the action and the corresponding sound-track films,
and it is necessary, therefore, to see that both punch marks are at
corresponding points.

To simplify handling separate sound-track and separate action,
numbers on the edge of the film, spaced one foot apart, are necessary.
These numbers are made in duplicate, and the same number that
appears upon the edge of the sound-track film appears also upon the
edge of the action film, identical numbers being in the same relative
positions from the start marks.

Two methods are used for placing the synchronizing edge numbers
upon the film: (1) by a machine specially constructed for the pur-
pose; (2) by printing the Eastman Kodak edge number (which is
already on the sound-track) upon the action film corresponding to the

366 How MOTION PICTURES ARE MADE [J. S. M. p. E.

sound-track. The latter method is used at this studio, and is regarded
as the more desirable. The difference in the cost involved is negligible,
yet the results attained by printing the edge numbers upon the posi-
tive are by far better, because of the permanency of the numbers.

With the dailies synchronized and properly numbered, they are
then shown to the director or other executives interested in the pro-
duction. When there are more than two takes to a particular scene,
the director, as a rule, selects the one he prefers. It is then set aside
for use in the picture, and the other takes are filed.

The efficient editor, as a rule, begins to edit his picture upon the
completion of a sequence. All the film of the sequence is assembled
in continuity order. This gives the editor an opportunity to familiar-
ize himself thoroughly with the film, and enables him to visualize
the cutting possibilities of the sequence. The editor's objective,
then, is to cut the sequence to the best advantage, utilizing such angles
as he feels will present the sequence in the most effective manner
upon the screen.

This procedure is continued as the director shoots the picture, so
that within a few days after the shooting has been completed, the
film is practically ready to be shown to him in what is termed "first
or rough cut." Most directors are thoroughly familiar with cutting,
and at times are of great help to both the picture and the editor.
The director, having made the picture, naturally may have his own
ideas with regard to the choice of angles for presenting the scenes.
In shooting the sequence, he may have been striving for certain dra-
matic or comic values in the situation, and quite often the editor may
have cut the sequence from a different point of view. This, naturally,
brings about discussion and, with an intelligent editor, the director
may sometimes find that the editor has already got the most out of
the situation with the film in hand. Best results are generally at-
tained when both the director and the editor work in close harmony
and are open-minded to suggestions.

The picture in first cut naturally runs considerably longer than the
general releasing length, and before final eliminations are made the
picture must be previewed ; in other words, presented to the public for
the public's reaction. All further cuts or eliminations are determined
by the effect of the picture upon the audience. Quite often certain
situations that look very appealing during the process of cutting fail
to impress the audience, and, conversely, situations that apparently
do not seem to carry much weight in the studio projection rooms

Oct., 1937] How MOTION PICTURES ARE MADE 367

sometimes evoke strong reactions from the audience. Thus, through
the medium of the preview, the director and everyone else concerned
are enabled to judge the actual screen values of all the situations and
business in the picture, and to decide which of them are not essential
or effective.

Before the preview is held, however, there is considerable mechani-
cal work through which the picture must go. First is the work of
embellishing and refining the various cuts in the picture. Then
there is the matter of adding sound effects and music, and also of in-
jecting certain photographic effects in the form of lap dissolves and
other tricks to which the picture may lend itself. Today, with the
perfection of optical printing, these effects which previously were pro-
duced upon the sets by the directors and which proved very costly
because of the time involved, are made on optical printers after the
picture has been completed. The preparation of sound effects and
incidental and other music and the dubbing of all the sound-tracks
into a single track for the purpose of a preview and later for release,
will be discussed later this evening by Mr. Edwin Wetzel.

With the introduction of sound into pictures, the latitude of the
editorial department has been lessened to the extent that where
originally the possibilities of realigning and recutting silent pictures
were unlimited, today we are confined more or less within the limits
of dialog. For that reason, preparation for the production of pic-
tures today is as vital as the actual shooting. Today, a script, before
it is put into production, should be practically letter-perfect. While
it is true that the average editor who knows his business thoroughly
can, as a rule, overcome certain deficiencies in dialog or action, or
both, by manipulating the film and sound-tracks, there are times
when even the ingenuity of the editor is of no avail ; with the result
that retaking the scene may be necessary, which, of course, means
additional expense.

The question of preparation applies also to timing the scenes on
the sets. In the silent days, a director had to watch the positions
of his actors when changing from one angle to another. He had to
make certain that he picked up his actors in the same positions when
changing the camera angle. Today, he must watch not only positions
of the actors but also note the words spoken when the actor is in a
certain position. Perhaps the greatest amount of grief that con-
fronts the editor of today results from the apparent carelessness of
some directors who overlook this vital point. To illustrate more

368 How MOTION PICTURES ARE MADE [J. S. M. P. E.

clearly: Assume that the director is shooting a scene in which an
actor is seated at a desk. The actor rises and walks across the room,
during which bit of action the actor speaks certain lines, both when
arising from the desk and when walking across the room. Now as-
sume that the scene was a long shot, and that the director now wishes
to shoot the same scene from a closer angle. Quite often we find
that when the closer shot was made, the actor did not speak the lines
corresponding to the action in the long shot. We may find that in
the long shot certain words were spoken while the actor was rising
from the deck; whereas in the closer angle the same words were
spoken while he was walking across the room — with the result that
the editor is compelled to choose the scene in the angle that will not
show a break in the action or the dialog, even though there may be a
decided advantage in going to the other angle.

Another point is the question of timing the dialog. Sound pictures
call for more close-up action than the silent pictures. In order that
the audience may be impressed by the delivery of lines, close action
is very necessary and at times the director when shooting his close-up
scenes may change his camera angle, showing the reaction of one of
the actors to the words of another. The dialog may be very rapid,
and the practice, as a rule, is to place the camera against the character
speaking the lines while the other character answers the lines off-
scene. When intercutting the two characters, and in order to regis-
ter certain facial expressions (unless the director has emphasized
these reactions and had the other characters off -scene pause suffi-
ciently to allow for them), the editor is at a decided disadvantage, be-
cause all that he can do in most instances is to cut from one angle to
the other while the dialog is going on continuously. The editor's
only alternative, as a rule, is to break the dialog by interspersing it
with silent track to allow for the pause. Sometimes that can be done,
but in most cases it is almost impossible, and it is needless to say that
timing the dialog should not be dependent upon the editor but should
be done on the set.

The practical director today is one who appreciates thoroughly
the limitations of cutting. Directors, however, differ considerably
in their method of shooting. Some directors safeguard themselves
by overshooting their pictures; that is, they shoot scenes from
many different angles, for protection. Other directors, being more
familiar with cutting pictures, cut most of their scenes in the camera.
Both methods have their advantages and disadvantages. From the

Oct., 1937] How MOTION PICTURES ARE MADE 369

producer's standpoint, overshooting pictures is very expensive; and
from the editor's standpoint, undershooting pictures causes untold
grief.

Many obstacles arise as a result of the director's trying to cut the
picture in the camera. In the effort to economize, the editor at
times finds himself in the position of being limited in cutting the
picture to the manner in which the scenes were shot by the director;
and unless the director is perfect in his timing, we find when trying
to connect certain scenes, that either the sound or the action does
not match. It is always a very good expedient for an economical
director, when attempting to cut his scenes, to overlap at least part
of the dialog and action when progressing his scenes through various
angles, and particularly to see that the dialog is timed perfectly with
the action in each angle that he shoots.

It is also a very good expedient for the director — from the editor's
viewpoint — to shoot long scenes from at least two or three angles. This
permits the elimination of dialog, if necessary. More than often we
find that a lengthy scene that reads well on paper does not hold when
recorded and shown on the screen, and unless the editor is protected
by having a variety of angles, he has no alternative other than to let
the scene run, as there is no means of cutting such a scene. Where
there is a doubt in the mind of the director as to the merits of a lengthy
dialog scene, he should by all means protect himself by shooting the
scene from various angles.

Some minor difficulties arise from time to time. One is the practice
of directors at the end of a scene of yelling into a camera and not allow-
ing the film to run a few additional feet. Sometimes the extra foot-
age is very valuable when trying to carry out lap dissolves or fades.
Some directors, likewise, have the habit, while a scene is going on, of
cueing the actors during the pauses of dialog, with the result that
sometimes the director's voice can be heard at the beginning of a
line of dialog.

These difficulties, as explained, emphasize all the more the impor-
tance of preparation in the production of pictures today. Prepara-
tion is the keynote to a successful picture.

The mechanical features involved in editing pictures are more or
less simple. They embody the use of the synchronizing machine,
the moviola, the splicing machine, and the rewinder. These de-
vices are very simple in operation, and require only a slight amount of
experience to attain more or less perfection in handling them.

370 How MOTION PICTURES ARE MADE [J. S. M. P. E.

We have explained previously the synchronization of film when
received from the laboratory, but, in addition to that each cutter is
supplied with a synchronizing machine, the purpose of which is to
enable him to keep his film in synchronism as he handles it. The
synchronizing machine can best be described as a shaft carrying any-
where from two to four sets of sprockets. The editor, while handling
his film, places both the sound-track and the action films over the
sprockets, which keep the film in sychronism at all times as he passes
the film from one reel to another during the editing. Should the
film by any chance slip over the sprockets, the editor has the
numbers on the edge of the film to guide him. This avoids the
necessity of going back to the original start mark in order to check
the sound-track with the action.

Experienced editors, however, do not use the synchronizing machine
much during the editing, but instead use the moviola. The practice
is to place the sound-track film beneath the action film, both passing
over the same sprocket wheel. Inasmuch as the sound-track film is
clear, the light passes through it, and the editor is able to handle
both sound-track and action films. He can also notice the modula-
tions on the sound-track, and the average editor after a little practice
becomes so adept and "film-wise" with regard to modulation of sound-
track, that he can almost be certain, by noting the modulation as
against the action, whether the picture is in synchronism or not.

Some editors, however, might find it necessary, when three or
more cameras are involved in shooting a scene and where there is
only one sound-track for the three or four scenes, to use a synchroniz-
ing machine that carries four sets of sprockets. The expert editor
will cut the action without the use of these "syncing" machines and
will match the film by action rather than by sound.

As the editor proceeds with his cuts the successive lengths of film
are temporarily fastened together by clips, after which the whole roll
is patched on a modern splicing machine. This machine enables
the assistant to make a thin patch that is generally more or less per-
manent. All assistant cutters are familiar with the use of these
splicing machines, and particular stress is laid upon the fact that the
loss of frames must be minimized. Every time a piece of action is
cut, there is a loss of one frame of film to allow for the patch. A
careless assistant cutter will lose three or four frames, and for each
frame that we lose we must insert spacers to keep the sound-track in
synchronism with the action. The reason for trying to save the

Oct., 1937] How MOTION PICTURES ARE MADE 371

frames is not so much with regard to the ultimate release of the picture
as for keeping the film in as good condition as possible for previewing.
Scenes that contain an over-abundance of black spacers require re-
prints so that the picture may be presented to the public in as clean
a condition as possible. Reprints, however, involve expense, and
whereas a single-frame spacer will pass through unnoticeably,
spacers of greater length will be very noticeable and generally will re-
quire reprinting.

Two types of patches are used : one covering the full sprocket and
the other covering the half sprocket. At this studio, we use the half-
sprocket patch, and find it very satisfactory. It seems to pass
through the projection machines more easily and has a long life. A
full-sprocket patch is inclined to tear apart. The question of re-
winding is very simple. Particular attention is called to the practice
of tightening the film while rewinding, which causes scratches. This
fault is avoided wherever possible.

The satisfactory assistant cutter is one who exercises speed, care,
and system in handling his film. System in a cutting room naturally
results in cleanliness. Film at all times should be kept filed in cans
and in fire-proof cabinets. Fire is a great hazard wherever film is
handled, and it is important that the amount of film on hand be kept
at a minimum. We can not emphasize this point too strongly. The
efficient editor, with the aid of an able assistant, seldom has much
film in the open at any one time.

The following mechanical devices comprise the essential fittings
of a cutting room: metal rewinding tables (each with one set of
rewinders and racks for filing small rolls of film ; with either artificial
or natural light in the background, facing the rack); steel cabinets
for filing excess film; combination sound and silent moviolas; film
bins; clips for fastening film together, preliminary to splicing; and
the necessary reels required in handling the film. Give an efficient
editor this equipment — and one pair of scissors — and no picture is
too great a task for him.

The writer has found it of great advantage to surround himself
with men who have had a number of years of experience back of them.
He finds that the longer the experience the greater their ability. An
editor, handling one picture after another, continually encounters
situations that perhaps have never confronted him before. Through
his experience he becomes thoroughly familiar with dramatic, comic,
and fast tempo situations. He becomes very confident in handling

372 How MOTION PICTURES ARE MADE [J. S. M. P. E.

the cutting of these situations and at times is able to create situations
in a picture that, from first appearances, the film would not permit.
Summing up, a thorough knowledge of film editing is perhaps the
best requisite for success in almost any branch of the production end
of this business, and particularly where direction is concerned. Di-
rectors who have risen from the ranks of editors are among the ace
directors of the business, having found that their knowledge of edit-
ing is of untold value to them in their work.

MR. TASKER : When the film editor has finally finished his work,
the next step is to prepare a musical accompaniment for the picture.
This is the work of Mr. Charles Previn, who will discuss the problem
of "Setting Music to Pictures."

SETTING MUSIC TO PICTURES

CHARLES PREVIN*

The scope of the subject of setting music to motion pictures is so
broad that I hardly know where to begin. However, the picture is
turned over to the music department, and we are told, "Well, here
is a picture. Can you have the music all ready for it by tomorrow?"

We then go over it with the director — if he is available, or the as-
sistant director, and others, and ask them to give us their ideas as to
where music would help the scenes in the picture. Then I get an as-
sistant cutter to time the sequences, which he does by running the
film through a footage counter to measure the length of each scene to
which we are required to put music. Then the length in feet is con-
verted into seconds of time, so, as an example, we find that we have two
minutes and thirty seconds in a given sequence to set to music. We get
a complete idea of the picture, what it is all about — the scenes, the
dialog in different spots; and in writing the music try to catch the
mood of the dialog and of the scene and plot.

Sometimes the director himself does not know exactly what is re-
quired. For example, I might be told that a certain scene was in-
tended to be dramatic, and that I should build up the situation with
dramatic music. Later, hearing the dramatic music I had put into
the scene, he might say that it was too "heavy," that I had taken the
scene too seriously; it was not what he wanted, but rather something

*Musical Director, Universal Pictures Corp., Universal City, Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 373

lighter. Then I would have to start at the beginning and do the
whole thing over again.

At this point, by way of illustration, a scene from "Wings over Honolulu" was pro-
jected upon the screen. The sequence showed the scene of a quarrel between two lovers,
and was projected first with a background of dramatic music and later with a back-
ground of music in a lighter vein.

The first music, whether you consciously recognized the fact or not,
makes a very serious matter out of what is a mere lovers' quarrel.
The situation was not very serious, and the picture should not give the
impression that it was. When the director saw the scene with the
dramatic music, he decided that it was too "heavy" and wanted us to
lighten it a bit. The second score was the result, with a great im-
provement, as you will agree.

All the music for these pictures is originally written for the pictures,
except in special instances such as in One Hundred Men and a Girl,
for which Mr. Stokowski plays the classical masterpieces. In most
of the pictures coming out of Hollywood nowadays, the music must
be originally written for them. Every picture presents new problems,
new thoughts, and new ideas, and the music to be written for it has,
I might say, no yardstick. As I mentioned before, we measure the
music by seconds, and for that reason we can not take any set music
and apply it to a certain length of film. Besides, if we used the old mas-
terpieces that have become so familiar, attention would be distracted
from the picture to the music, because of familiarity with the music.

In writing the music it is very necessary to do things mechanically
up to a certain point, and then to forget the mechanical element.
Writing the music into a given space of time is the mechanical part,
but we must get. the feeling into the scene that the director means to
portray.

At this point, and for further illustration, the scene from a picture "Parole" was
projected, showing the effect of the background music in heightening the dramatic in-
tensity of the scene.

MR. TASKER: And now at last all the essential elements of the
completed picture have been prepared, and we are ready to assemble
a final sound-track to accompany the action. A number of persons
are involved in this final step, including music cutters, sound-effects
cutters, and the dubbing crew, and in charge of all these is the dubbing
mixer. This final step will be described by Mr. Edwin Wetzel,
dubbing mixer.

374 How MOTION PICTURES ARE MADE [J. S. M. p. E.

ASSEMBLING A FINAL SOUND-TRACK
EDWIN WETZEL*

The dubbing or re-recording process constitutes one of the final
operations in producing a motion picture. It consists in blending
additional sound effects and music with the dialog in order to match or
enhance the pictorial effect that the director has achieved through
the use of the camera.

The process was developed shortly after the advent of sound. It
was discovered that the necessity of moving the camera from one lo-
cation to another, and the impossibility of predicting exactly how the
picture should finally be edited, made it impossible to maintain a
constant level or any semblance of smooth continuity in the added
effects or background music if they were recorded at the time the
picture was being photographed.

When the picture is completed, so far as actual photographing is
concerned, and when the editorial department has finished its work,
the picture is then shown to the sound effects and music depart-
ments, at which time is decided the nature of the effects and music
that are to be added.

The effects department then refers to the sound library to deter-
mine which of the required effects are available from stock and which
must be especially recorded to complete the picture in question.
When this material is made available, it is then necessary for the
sound-effects cutter to synchronize the various effects to the picture,
and the number of sound-effects tracks he must build depends upon
the number of effects that are to overlap in any one situation or se-
quence of the picture.

At this point a scene from "Wings over Honolulu" was projected, with dialog only,
just as it was photographed and recorded on the set. The scene showed the interior
of a house where a birthday party was in progress, Miss Wendy Barrie descending
the staircase to join the party. A storm arises outside, during which Miss Barrie
and Mr. Kent Taylor step to the veranda outside the house. A shift of scene shows
an aeroplane landing near the house in the midst of the storm.

During Mr. Wetzel's analysis of the scene, short samples of the individual sound-
effects tracks were reproduced to illustrate the points made in the analysis. At the
end of the presentation the scene was projected again, this time with all the various
effects mixed together with the dialog at the proper points and in suitable intensities,
just as they would occur in the finished picture.

Analyzing the scene we find that in the interior of the home we need
additional background voices coming from the guests (voices) and
*Dubbing Mixer, Universal Pictures Corp., Universal City, Calif.

Oct., 1937] How MOTION PICTURES ARE MADE 375

dance music (music). Although this is a birthday party there is no
pictorial evidence of the fact, so we must establish the fact off-stage by
having an orchestra play and the crowd sing Happy Birthday (music
and song) which evokes the laughter from Wendy Barrie on the stair-
way.

Later, the flash of lightning at the window establishes the fact that
a storm is approaching, so a clap of thunder might be used (thunder] .
Now we cut to the exterior, and perhaps the chirping of crickets
might add to the general effect (effect] . Of course, we must continue
the thunder and the music ; but now the music accomplishes two pur-
poses : it adds to the romance of the veranda scene in addition to in-
dicating that the party is still in progress inside.

The significance of the succeeding effects is quite interesting. As
Kent Taylor finishes the line, "Are you waiting for a knight to ride
up on a white charger and carry you away?" everything happens at
once — a terrific flash of lightning accompanied by thunder, the rain
falls, and you see an aeroplane approaching (effects; singly, then com-
bined}. The combined sound-effects are used not only to match the
action on the screen but to act as a fanfare ushering in the hero of the
story.

Note that while all this confusion is going on we must stop the
music, because the director wants to create the impression that when
the plane lands the two men will think that they are lost. If they
were to hear the music coming from the house there would be no
reason for believing so.

MR. TASKER: It has been said that all that the picture industry
has to sell are a few flickering shadows and a few undulated sound
pressures. This evening we have taken you through the "House of
Magic" where those shadows and pressures are created and where
they are given vitality and meaning. We hope you enjoyed it, and
we who presented this program to you were very, very glad to do so.
I should like to express our own appreciation to a number of persons
whom you have not seen tonight, but who have labored behind the
scenes to make this meeting a successful one. A large number of
people have contributed their time and efforts here this evening, as
well as on previous evenings to prepare this program. They were
very glad to do it for the Society, as typifying the spirit of the New
Universal by the way in which the technical staffs have put their
efforts together in this demonstration this evening.

REPORT OF THE SUB-COMMITTEE ON PERFORATION

STANDARDS*

Summary. — The Sub -Committee has investigated the possibility of adopting the
SMPE standard perforation for negative film, and has come to the conclusion that vari-
ous factors, especially the stock of background films, makes it impossible to use
the SMPE standard perforation universally.

The Committee now proposes that the rectangular perforation proposed by Howett
and Dubray in 1932 be adopted as the standard perforation for both negative and
positive. This perforation would operate satisfactorily on all apparatus designed
for the Bell & Howett perforation, and should give little or no trouble on apparatus
designed for the SMPE standard perforation.

At the Fall Convention of the Society in 1931, a proposal was pre-
sented by A. S. Howell and J. A. Dubray, recommending the estab-
lishment of a single universal standard perforation. The Standards
Committee took the matter under advisement and at a meeting held
on June 2, 1933, a resolution was passed adopting the present rec-
tangular positive perforation as a universal standard.

Matters then remained at a standstill, mainly because of the diffi-
culties encountered in inducing the owners of equipment in the field
to alter their apparatus to conform to the present positive perforation.
Cameras, in particular, presented the greatest obstacle because of
their wide-spread use throughout the world and the difficulty of reach-
ing the travelling cinematographers.

It is the purpose of this report to discuss the registration of film in
the various kinds of equipment in use in the camera and laboratory
fields, comparing the behavior of the present perforations and present
means of registration with the behavior of the perforation proposed
herein and the same means of registration; extending the discussion
to the behavior of the proposed perforation and the proposed improved
means of registration.

DIMENSIONS OF PRESENT AND PROPOSED PERFORATIONS

The dimensions of the proposed perforation can be simply expressed
as follows :

* Presented at the Spring, 1937, Convention at Hollywood, Calif.; received
June 25, 1937. Prepared at the request of the Standards Committee.
376

SUB-COMMITTEE ON PERFORATIONS

377

The universal perforation for both negative and positive film shall be rectangu-
lar, shall be 0.110 inch wide by 0.073 inch high, and shall have rounded corners
of a radius of 0.013 inch.

The width of the proposed perforation is to remain the same. Its
height is to be equal to the height of the present negative perforation
and 0.005 inch less than that of the present positive. The radius of
the rounded corner is to be within the chord height of the radial portion
of the present 35-mm. negative perforation. Upon the fulfillment of the

FIG. 1.

Present and proposed perforations. In the lower right-hand corner
the three perforations are superimposed.

last condition depends the possibility of using the new perforation,
without altering the existing apparatus, as effectively as the present
dual standards. Fig. 1 shows the present and proposed perforations.
In the lower right-hand corner of the illustration are the three per-
forations superimposed, showing the coincidence of the radius of the
rounded corners with the chord height of the radial portion of the
present negative perforation.

REGISTRATION IN CAMERAS AND SPLICERS

Pilot-pins of cameras are at present designed to fit the negative
type of perforation as shown at the upper left of Fig. 2. The present

378

SUB-COMMITTEE ON PERFORATIONS [J. S. M. P. E.

pins could be used as effectively in the camera to register negative
films perforated with the proposed perforation, as illustrated in the
upper right-hand corner of Fig. 2, and the driving pins of the camera
movement would perform similarly with both perforations. Equip-
ping the cameras with the proposed driving and pilot pin, as illus-
trated in the lower right-hand corner of Fig. 2, would result in an ad-
vantage because of the decreased strain imposed upon the film as a
result of variation in the dimensions and location of the perforations.

FIG. 2. Relation of pilot-pins to perforations.

The proposed pilot-pin would also assure lateral as well as longitu-
dinal registration, particularly in camera mechanisms not equipped
with edge-guiding devices.

In this respect it may be noted that perforation by the Bell &
Howell perforator is accomplished with a great degree of precision,
there being practically no tolerances and the location of each succes-
sive four pairs of perforations being controlled by four sets of pilots
engaging in the four pairs perforated immediately previously.

Since the proposed pins would bear on all four sides of the perfora-
tion, greater assurance of perfect registration under all conditions
would be. gained. It is to be noted, however, that the present pilot-
pins would not be less effective with the proposed perforation than

Oct., 1937] SUB-COMMITTEE ON PERFORATIONS 379

with the present negative perforation. This would not be so if the
present positive perforation 0.078 inch high were used in conjunction
with pilot pins 0.073 inch high, because the danger of error in longi-
tudinal registration is as great as the difference between the height of
the pin and that of the perforation.

It must be borne in mind that the adoption of the universal per-
foration 0.078 inch high would of necessity require the installation of
new pins in all cameras, whereas the adoption of the proposed per-
foration 0.073 inch high would not impose such change of pins as an
absolute necessity, thus easing the burden on the owners of cameras
scattered widely throughout the world. It would also be impossible to
reach all cameras in use with any degree of promptness, and the
consequences that may flow from this fact would be a serious re-
sponsibility for the Society.

One of the most important and relatively recent advances in special
process cinematography is the background projection method. Per-
fect steadiness of projection and perfect registration in the camera are
essential requisites for the success of the process. Experience has
proved that very accurate registering mechanisms are required in
both cameras and projectors, and at the present time two alterna-
tives are possible: (a) either the print to be projected must be on
positive film perforated with negative perforations, or (b) the original
negative must be photographed on negative film perforated with
the present positive perforation and the camera movement equipped
with positive driving and pilot pins. The use of different perfora-
tions for negative and positive records always presents the possibility
of inaccurate registration, which may act to the serious detriment of
the finished picture.

The establishment of a single universal perforation would remedy
once and forever the anomalous situation now existing. In fact,
all special photographic processes, such as multiple exposures, glass
shots, color-separation processes, cartoon making, and many
others too numerous to mention can be performed to the satisfaction
of all their technical requirements and with assurance of perfect
registration upon the adoption of the proposed perforation and the
proposed pilot-pins.

INACCURACIES UNDER PRESENT CONDITIONS, AND THEIR ELIMINATION
THROUGH A UNIVERSAL PERFORATION

It is almost needless to point out that color cinematography would

380

SUB-COMMITTEE ON PERFORATIONS [J. S. M. P. E.

find great advantages in the proposed perforations and pins. In the
various color processes using multiple negatives^ success in projection
begins with proper registration, which can be done only by properly
locating the film in the film-propelling mechanisms of all the apparatus
used in the various operations of the process. The slightest inac-
curacy of registration in any of these operations irremediably spoils
the picture, and more precise means of registration would solve many
problems, eliminate disappointments, and save much time and
money.

a

O

a

a

a

a

Sf1

a

[ J I \— PE/TFCCr ffllf£

\ no'\ \ m'

a

a
a

o

a

FIG. 3. Errors of alignment due to splicing.

SPLICERS

Splicers are now equipped with pilot-pins for either negative or
positive perforations. It is only in the large laboratories, however,
that a distinction is made between the one type of machine and the
other. Most small laboratories use splicers equipped with negative
pilot-pins for splicing films having either negative or positive perfora-
tions. It is obvious that serious errors may result from this pro-
cedure. These errors are illustrated in Fig. 3.

The upper left-hand corner of Fig. 3 illustrates the error occurring
when two films having the present positive perforations are spliced
with a splicer equipped with negative pilo't-pins. The inaccuracy of

Oct., 1937] SUB-COMMITTEE ON PERFORATIONS 381

alignment is evident. More serious is the error that occurs when a
film having the present positive perforations is spliced to a film
having the present negative perforations, as illustrated at the lower
left-hand corner of Fig. 3. A universal perforation and proper pilot-
pins would completely eliminate these errors, and there would be no
need of discriminating between splicing machines, except as regards
setting the splicer cutting blades to the proper width of the splice.

REGISTRATION AT MAIN SPROCKET OF CONTINUOUS PRINTING MACHINES

The printers most used in the film processing laboratories are of
the continuous type, and guide the film at the printing aperture by
means of a 64-tooth sprocket. The sprocket diameter, pitch, and
form of the teeth, and the arc of contact of the film with regard to the
number of teeth engaged, together with the carefully adjusted film
tension, provide accommodation for the shrinkages of both negative
and positive films, predetermined, with reasonably extended per-
missible tolerance for undetermined shrinkage. This controls the
longitudinal registration of the film, in all its complexities, with suffi-
cient accuracy, but does not assure constant and precise lateral loca-
tion of the film. Because of the double perforation standards and
because of the variable shrinkage of the film, the sprocket-tooth
form is necessarily a compromise designed to cope with undesirable
conditions.

In the upper left-hand corner of Fig. 4 is shown a comparison of a
main printer sprocket tooth engaging the negative perforation and a
positive perforation, the latter shown in dotted lines. The thickness
of the tooth is calculated to provide proper clearance for predeter-
mined shrinkages, and its faces are designed to offer bearing surfaces
on the sides of the negative perforation so that the negative film will
be well located and well guided throughout its run, and the possible
lateral tolerances be so small as to be not only negligible but suitable
for smoothly stripping the film from the tooth. The positive perfora-
tion, on the other hand, because of its rectangular shape, presents the
possibility of two locations for the sprocket tooth, with either side of
the perforation in contact with the tooth as illustrated in the lower
left-hand corner of Fig. 4. The full-lined perforation represents one
condition and the dotted-lined perforation the other, the difference
in lateral registration being as great as 0.004 inch.

This does not mean that once the printer is threaded, the film may
sway laterally back and forth, but it does mean that in the threading

382

SUB-COMMITTEE ON PERFORATIONS [J. S. M. P. E

operation the film may be placed in either position. The variation
in the position of the film is not seriously detrimental, considering the
present dimensions of sound-films, because the difference between the
width of the sound record and that of the scanned area offers ample
protection against the 0.004-inch possible difference in locating the
positive film on the printer sprocket. Push-pull sound-track dimen-
sions do not, however, allow such protection, and the maximum toler-
able difference in lateral location of the film is reduced to 0.0015 inch.

FIG. 4.

Engagement of printer sprocket teeth with proposed and present
perforations.

It is true that the present practice is to re-record the original push-
pull sound record, but to all indications direct reproduction of the
push-pull track in theaters is only a matter of time and will be stand-
ard practice in the majority, if not in all, auditoriums in the not
distant future.

The adoption of the proposed universal perforation for both nega-
tive and positive films will permit altering the teeth of the main
printer sprocket to the form shown at the right of Fig. 4. This
would assure ample bearing surface on the side of the perforation,
with a possible difference of 0.001 inch in laterally locating the film
while accommodating a negative film shrinkage of 1 per cent.

Oct., 1937] SUB-COMMITTEE ON PERFORATIONS 383

It may be mentioned here that present sound-recording film
carries the present positive rectangular perforation, and that some
continuous printers have been equipped with sprockets the teeth of
which have the form that would be adopted as standard for printers
with the acceptance of the proposed perforation. This is essentially
true of the sound-head of the Bell & Howell automatic printer and of
some of the Bell & Howell model D printers, which have been as-
signed solely to sound printing in some of the major laboratories.
However, this procedure eliminates the possibility of interchangeably
printing sound-track or picture area as desired, and is obviously un-
desirable in all instances and impossible in small or relatively small
laboratories where economies of space and capital investment are of
major importance.

Again, as in other apparatus, the recommended modification of
printer sprocket design would be a marked improvement in the print-
ing process, but would not be essential. It is to be noted, however,
that locating on the unmodified printer sprocket two films having
rectangular perforations requires some care. Both films, negative
and positive, should be so aligned that the sides of one row of perfora-
tions, preferably those on the sound side, are in contact with the
sprocket tooth, to avoid the possibility of error in the lateral location,
which can be as great as 0.008 inch.

INTERFERENCES OF SPROCKET TEETH WITH PERFORATIONS

The most serious objections offered to adopting the proposed
universal perforation were expressed by projector manufacturers, and
were based upon the assumption that because of the reduced height
the proposed perforation would interfere with the proper running of
positive film that had shrunk considerably. The universal perfora-
tion was proposed to the Society in 1931, after an extensive investi-
gation of the then-prevailing shrinkage characteristics of positive
film, and particularly of films that were nearing the last stages of
their useful lives and in which the shrinkage had become considerable.

It is an accepted and proved fact that present films are much stabler
and shrink less than films of past years. Improved methods of
handling films in exchanges and in projection rooms, and a better
understanding and appreciation of the necessity of handling films
properly have in recent years practically eliminated the possibility
of finding prints in theaters that have shrunk so badly as to prevent
their use in a projector without mishap. Furthermore, it is quite

384

SUB-COMMITTEE ON PERFORATIONS [J. S. M. P. E

impressive to note that Technicolor release prints are printed on films
bearing the present standard negative perforation 0.073 inch high,
and that no inconveniences or trouble have ever been encountered
in this respect in their long-run projection lives.

The left portion of Fig. 5 shows the possibilities of interference of
the projector sprocket teeth with the proposed perforation. The
upper left section of Fig. » illustrates the condition that exists when

Oct., 1937] SUB-COMMITTEE ON PERFORATIONS 385

unshrunk 35-mm. film bearing the proposed perforation is driven by
a 16-tooth feed or intermittent sprocket of SMPE standard design.
Exact registration is maintained, as the perforation pitch is equal to
the pitch of the sprocket teeth.

However, such a condition is never encountered in actual practice,
and the second section of Fig. 5 shows that with a film that has
shrunk lx/2 per cent, which is the maximum shrinkage encountered
today, tooth interference takes place in the 16-tooth feed and inter-
mittent sprockets at the 8th tooth. The maximum number of teeth
in mesh in most projection machines is 6 for the feed sprocket and 5
for the intermittent sprocket. With the proposed universal perfora-
tion and the present standard design of sprocket teeth, there is, there-
fore, a considerable margin of safety to cope with the very rare in-
stances in which films that have shrunk more than ll/2 per cent
would have to be projected.

The condition is different with regard to the projector take-up
sprocket, because the function of the latter differs considerably from
that of the feed and intermittent sprockets. The third section on the
left of Fig. 5 shows that unshrunk 35-mm. positive film bearing the
proposed perforations would encounter interference with the 8th
tooth of the take-up sprocket. The last section of Fig. 5 shows that
enact registration is attained with film that has shrunk \l/z per cent.

It is quite apparent from these data that no ill effects are to be ex-
pected from the adoption of the proposed perforation with regard to
projection apparatus now available and in use. With a view to the
future, the proposed perforation would offer possibilities of guiding
the film in projectors more effectively and exactly by letting the pre-
cisely located sides of the perforations control the position of the film
instead of guiding the film on the edge, as is the present practice.

Referring to the right-hand side of Fig. 5, the top section shows
that negative film that has shrunk Y4 per cent would be ideal for a
32-tooth camera sprocket. The second section on the right-hand
side of Fig. 5 shows that except for unshrunk positive raw stock the
registration would be perfect for the 64- tooth main printer sprocket.
The third section shows that negative film shrunk l/% per cent would
interfere with the 81st tooth of the 64-tooth printer sprocket, and
that a l/3 per cent shrinkage would be ideal. The lowermost right-
hand section of Fig. 5 illustrates the conditions encountered with the
64-tooth main printer sprocket and an unshrunk positive film with a
Va per cent shrunk negative.

SUB-COMMITTEE ON PERFORATIONS [J. S. M. P. E.

LIBRARIES OF STOCK NEGATIVES

The problem of using stock negatives bearing the negative type of
perforation is perhaps the most difficult to solve, particularly in such
cases where it is necessary to intersperse such negatives with negatives
bearing the proposed universal perforation. The problem to be
faced by the industry would have to be faced regardless of the di-
mensions of the rectangular perforation ultimately adopted as
universal, whether the height be 0.073 or 0.078 inch; and would be
more serious with the former, which is the one recommended in this
report. However, the advantages to be derived from adopting the
0.073-inch perforation in all other phases of motion picture work are
so outstanding that it is believed that they justify taking means of
adapting the existing stock negatives to a new perforation technic.

The proponents of the proposed perforation in 1931 pointed out
the possibilities and suggested means of reperforating the stock nega-
tives with the proposed universal perforation. The question of re-
perforating is rather serious, as at best it would be rather costly and
some risk would be involved, particularly if the stock negatives to be
reperforated are old and overshrunk. It is believed that the re-
markable progress made recently in duplicating negatives offers the
logical solution of the problem, and perhaps the most advisable.
Duplicating stock negatives or using them for reprinting when the
two types of perforation are not interspersed, could be done on a re-
serve printer the sprockets of which have not been altered to the new
perforation. This machine could be retained during the transition
period.

This analysis of the proposed universal perforation and its advan-
tages are submitted to the Society and to the Standards Committee
with the recommendation that the proposed perforation be adopted
at as early a date as possible, so that new avenues may be opened for
further advances in the technic of motion picture making in its many
phases. Progress in the photographic, sound, and color fields will
be hampered and retarded if the present dual standard is permitted
to exist for any considerable length of time.

J. A. DUBRAY, Chairman

DISCUSSION

MR. SKINNER: It will be much easier to make a continuous sprocket for
printing with this method because a flat side of an accurate part will be available,

Oct., 1937] SUB-COMMITTEE ON PERFORATIONS 387

and we shall not get into the embarrassing situation- of having to use some sort of
turning tool to cut the teeth in order to get the Bell & Howell perforations.

MR. TOWNSLEY: It is slightly easier to produce an accurate continuous
sprocket with this new tooth.

MR. SKINNER: Have any instruments been made to punch these perforations?

MR. TOWNSLEY : I believe the Eastman Kodak Company has a set of dies for
the new perforation. It is no more difficult to make punches and dies for this
perforation than for the present rectangular positive perforation. The perfora-
tion has been made for a number of years, and the punches present no difficulty in
manufacture.

Except for the most rigid requirements, we believe that the present negative
pilot-pin will be perfectly satisfactory for this perforation. There is, of course,
the possibility that continual use of a negative on a pilot-pin machine such as a
step printer will result in slight wearing of the perforations.

MR. FRAYNE: It so happens that I am a member of a Committee of the Acad-
emy on sound-track dimensions in push-pull work, and the question has been
raised as to whether or not, in printing, we should use the sprocket or the edge-
guide. With this new sprocket in the printer the guiding is done by the tooth,
and then in the reproducing machines by the edge-guide, and we finally get into
trouble because of errors in the perforations of the film. Has the Committee
given any thought to using the edge-guide instead of the sprocket?

MR. TOWNSLEY: I believe the Committee has given that some thought.
There is on the market a continuous printer the sound sprocket of which is
equipped with this proposed tooth. Using sound recording stock bearing the pres-
ent rectangular perforation, perfectly satisfactory prints were obtained. If a prin-
ter such as the Bell & Howell model D printer is used, with teeth designed to
accommodate both positive and negative perforations, excessive side weave results;
but with the proposed rectangular tooth, which registers by means of either side
of the rectangular perforation, the weaving was insufficient to cause trouble in the
projection, even though the guiding in printing was done by the sprocket teeth
and in reproduction by the edge of the film.

MR. REMERSHEID: What is the difference in width of this sprocket tooth com-
pared with the old one?

MR. TOWNSLEY: The old or negative sprocket tooth, the tooth designed for
the Bell & Howell perforation, measures 0.106 inch across the outside of the tooth,
and the proposed tooth measures 0.1089 inch, or practically 0.109 inch across the
tooth, so that there is a maximum displacement of the positive with respect to
the negative on the proposed tooth of only 0.002 inch.

MR. TASKER : I wonder whether the fact that the non-slip printers are ap-
parently destined to handle most of the sound-film of the future, does not mean
that we are no longer very much interested in sprocket-hole guiding in printing
sound-track.

MR. TOWNSLEY: The advantage of the proposed perforation is that it will
run on any present equipment just as satisfactorily as the old double
system of perforations. The results with the new tooth are superior to the results
attainable with either the proposed perforation or the old perforation on the
present equipment designed for the combination of positive and negative perfora-
tions.

A NEW DYNAMIC LIGHT-VALVE*
E. GERLACH**

Summary. — A description of a new type of dynamic light-valve with oil-damped
mirror used in the "Eurocord" recording equipment. Damping by oil, though in-
fluenced by temperature, is compensated automatically.

Electrodynamically actuated vibrating mirrors, operating accord-
ing to the principle of the "Blondel" type of loop oscillograph, have
a number of advantages over vibrating mirrors actuated by oscillating
iron armatures. The driving force is very accurately proportional to
the current, and, furthermore, acts directly upon the vibrating mirror.
Indications of hysteresis and other amplitude distortions are com-
pletely eliminated. When the oscillatory system is at rest no forces
act upon it other than a strong elastic force that maintains the oscil-
latory system very steadily at its zero position, the value of which
can accurately be determined. Another advantage is that the loop
represents an ohmic resistance over the whole frequency range, be-
cause any reactions caused by oscillation of the two ribbons of the
loop may be practically neglected, and, as a result adaptation to the
amplifier becomes quite simple and can be effected with a high degree
of efficiency. Considerations of this sort made it appear worth while
to endeavor to improve the loop oscillograph as applied to the field
of sound-films.

A deciding factor in determining the dimensions of a design de-
scribed herein was the size of the vibrating mirror. From optical and
photographic considerations, an area of 2.5 sq. mm. was decided upon,
preferably circular or square, so as to take full advantage of the light-
beam. A rectangular mirror having its longitudinal axis parallel to
the ribbons would be desirable, as such a shape would reduce the
moment of inertia to a minimum. These two conditions being con-
tradictory to each other, a compromise was effected in a rectangular
shape having an area of 2.5 sq. mm. A mirror so shaped is well

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received June
30, 1937.

** Klangfilm Gesellschaft mit beschrankter Haftung, Berlin.

388

A NEW DYNAMIC LIGHT- VALVE 389

covered when illuminated by the usual tungsten coiled-wire filament ;
however, the moment of inertia is not small enough to allow locating
all the resonances above the upper limits of 10,000 cps. Of course, it
is advisable to place the fundamental frequencies as high as possible,
if not altogether outside the range, thus avoiding complicated dis-
tortion-correcting devices in arriving at a flattened frequency curve.
Simple damping answers the purpose. The main portion of the
frequency curve, right from the beginning and under all circum-
stances, appears as a straight line. Considerations of this sort led
to choosing for the damped loops a fundamental frequency of 7500
cps., and resulted in a frequency curve practically flat up to 10,000
cps. This was accomplished by a damping method to be described
later, which in no way was influenced by temperature changes.

In arriving at the dimensions of the ribbons it is important to use
as little power as possible for operating the oscillograph so as to per-
mit building apparatus that would be light in weight and easily
portable. However, since in the present case the power required is
less than 0.5 watt, there is no advantage in reducing it still further,
as the weight thus gained is insignificant compared with that of the
entire apparatus. There is therefore no necessity of insisting upon
a loop system having a maximum efficiency from an electromechani-
cal standpoint; but it is quite essential to make use of as much power
as possible for operating the apparatus in order to gain a large rotat-
ing angle. The greater the angle through which the vibrating mirror
operates, the easier it is to effect a favorable and reliable construc-
tion of the comb-shaped shutter and the noiseless shutter. The
power carried by the loop is not governed by considerations of stress
and strength, but solely by the heating effect of the current. Exces-
sive current impulses of short duration therefore are not important.
The design of the ribbons is therefore determined solely by the in-
crease of temperature resulting during steady full modulation. For
that reason an effort should be made to dimension the ribbons so as
to present large heat-radiating surfaces.

Further design features of the apparatus depend upon the following
considerations: The thickness of the ribbons must be kept within
such limits as to prevent their tendency to uncoil from causing irregu-
larities in the deflection of the supporting spring. Furthermore, the
width of the magnetic air-gap is determined by the width of the
mirror, as the latter is located at the most effective point in the length
of the ribbons — the center. It is not possible to make the central

.390

E. GERLACH

[J. S. M. P. E

part of the air-gap narrower than is required by the width of the
mirror; . and it is hardly worth while to provide specially shaped pole-
pieces, considering also the decrease of efficiency near the edges of
the ribbon.

Taking all this into consideration we arrive at a shape of loop as
shown in Fig. 1. The aluminum ribbons are clamped along the line
2-2, at which point, also, the current enters and leaves. The ribbons
are made of round wire, flattened in a special device. At 6, where
the material is left rounded, the loop can easily be suspended from a
hook, which transfers to the ribbons the constant tension of a flat
spring. At section 4-4 the ribbons pass over a bridge, which de-
termines the oscillating length 2-4. The unused portions of the

FIG. 1. (Left) Diagram of loop with mirror.

FIG. 2. (Right) Means of obtaining additional damping of the

loop.

ribbons, representing a total loss, are limited to the short bend at the
hook. Cementing the mirror 3 to the ribbons would result in optical
distortion caused by deformations at great amplitudes. Two causes
are responsible for this: first, mechanical distortion of the ribbons
during oscillation, since the twisting naturally would react upon the
mirror; and, second, distortion caused by heat, which would in-
fluence the entire system of mirror, cement, ribbons, etc., due to the
differing coefficients of expansion of the several materials. For
these reasons the mirror is fastened to the ribbons at two points only,
as indicated in Fig. 1 by the small circles 5. At these spots, small
round pads punched out of impregnated paper are inserted between
the mirror and the ribbons by means of cement that will not soften
at temperatures lower than 100° C. The mirror is cemented to the
ribbons in a special device and at the required high temperature, so
as to assure positioning it correctly and exactly parallel to the ribbons.

Oct., 1937] A NEW DYNAMIC LIGHT- VALVE 391

However, no matter how carefully the cementing is done, inac-
curacies will occur during the process, especially as regards the ab-
solute parallelism of mirror and ribbons. Two means for a final and
accurate optical adjustment have therefore been provided, to be made
after the mirror has been cemented in place, by which the mirror can
be turned slightly around its longitudinal and transverse axis. The
bridge 4-4 (Fig. 1) has been so arranged that it can be raised and
lowered by means of a screw, turning the mirror about its transverse
axis. The mirror can be turned also about its longitudinal axis, for
which purpose the bridge, hook, and tension spring are mounted on a
brass plate resting upon two balls and able to swing around. The
longitudinal axis of the mirror coincides with the centerline through
the balls. Any adjustment of the screw, therefore, will swing the
brass plate around, thus causing slight torsion in the loop, which, in
turn will cause the mirror to swing around accordingly.

'/ fe *3

FIG. 3. Amplitude of bimetallic spring:
ordinates, distance of plate; abscissas, tempera-
ture.

In order to damp the natural oscillations, the loop is submerged
completely in oil, and for this purpose the housing of the loop is al-
most completely oil-filled. Part of the housing is left free from oil
so as to permit the oil to expand with rising temperature; but re-
gardless of the position of the housing, there is no possibility that any
oil bubbles will arise to cause interference. As shown later, there is
very little space left for the oil in front of and behind the loop, and
therefore the capillary forces existing will prevent air bubbles from
entering these narrow spaces.

For damping the loop a rather thin oil is used having a low con-
gealing point so as to make the system work even at low temperature.

392

E. GERLACH

[J. S. M. P. E.

For normal temperatures, damping by oil alone would not be sufficient,
so additional means of damping have been provided : one adjustable in
itself, but initially adjusted for a fixed amount of damping; the
other adjusted automatically according to the prevailing tempera-
ture. In both cases the desired increase of damping, i. e., friction, is
achieved by moving small plates closer to the loop, thus decreasing
the oil-space in front of or behind the loop. As the space for the oil
becomes narrower, resistance to its flow increases, which, in turn, in-
creases the damping of the mirror since the latter can move only when
the oil has a chance to move with it. In such manner quantities of

FIG. 4. Arrangement for temperature
calibration: lower compartment, pump;
upper compartment, loop.

oil oscillate with the loop, but their movements serve still another
purpose.

Near the edges of the ribbons and the mirror, small eddy-currents
occur in the liquid, resulting in considerable circulation of the oil.
This aids materially in cooling the loop, especially if (and such is here
the case) the metal submerged in the liquid is a good conductor of
heat.

Fig. 2 shows schematically the arrangement of the fixed and the
variable damping method. The mirror 1 is fastened to the ribbons
2 (shown in Fig. 2 in side view), and the surface of the lens 3 is moved
more or less toward the mirror by means of a screw-thread 4, until
the desired amount of damping has been effected. On the opposite
side, a copper plate 5 is arranged so that it can be moved toward the
ribbons 2. This is done by means of a bimetallic spring 6, against

Oct., 19371

A NEW DYNAMIC LIGHT- VALVE

393

which the guide rod 7 of the copper plate is pressed steadily by the
flat spring 8.

Rising temperature causes the bimetallic spring to bend, thus
decreasing the distance between the ribbons 2 and the damping plate,
while the friction of oil increases as compensation for the decreasing
viscosity of the oil.

In order to provide adequate compensation within greatly varying
temperatures it became necessary to subdivide the movement of the
bimetallic spring into two ranges. In one range the spring is much
more sensitive to temperature than in the other. This is achieved by

Dnibtl *"-

FIG. 5. Amplitude vs. distance of damping
plates: ordinates, amplitude; abscissas, distance of
damping plates in n. (Lens distance SOM; +5° C;
frequency 7500 cps. ; sollwert — rated value.)

means of the regulating screw 9 (Fig. 2). The situation is shown
schematically in Fig. 3, curve 1 of which indicates the movement of
the damping plate as it would be for ideal temperature compensation.
On the X axis are laid out the different temperatures, on the Y axis
the distances of the plate from the ribbons. The general characteris-
tics of the curve are readily understood : At very low temperatures
the plate should remain at an infinite distance, because no additional
damping is needed. With rising temperature this plate at first ap-
proaches very rapidly, later more slowly, because its influence upon
damping is little at the start and increases more and more the closer
it approaches. The curve 1 approaches therefore the zero axis
asymptotically. The movement of the bimetallic spring is in exact
proportion to the temperature, as shown in Fig. 3 by the two straight

394

E. GERLACH

[J. S. M. P. E.

lines 2 and 3: 2, which is rather steep, pertains to the temperature
range tik; 3, less inclined, and corresponding therefore to a lower
sensitivity to temperature, pertains to the temperature range from
fe/s. The steady and regular curve 1 is, therefore, approximately
replaced by two straight lines intersecting at a point corresponding to
the temperature k- At that temperature the bimetallic spring just
touches the adjusting screw 9 (Fig. 2), which keeps the movements
within certain limits. It is evident that the inclinations of the
straight lines 2 and 3 in Fig. 2 are governed entirely by the dimen-
sions of the bimetallic spring and by the position of the screw 9.

FIG. 6. Temperature vs. distance of damping plates:
ordinates, distance of plates; abscissas, temperature
(centigrade). (Lens distance 85/x; frequency 7500 cps. ;
sollwert = rated value.)

Fig. 3, in the upper right-hand corner, shows schematically the ex-
treme positions of the bends. The bimetallic spring is a combination
of two different kinds of steel. For adjustment of the spring cor-
responding positions of the screw 9 are provided.

Final inspection of the instrument and its temperature calibration
are done by means of the arrangement shown in Fig. 4. Water or
other liquid at given temperatures circulates through the apparatus ;
the oil container, surrounded by a constant flow of water, being left
open so as to make possible calibration with a full oil container. The
oscillations are observed from below.

Curve 1 of Fig. 3 represents the movements of an ideally operating
damping plate, but a further correction is necessary if it is desired in

Oct., 1937]

A NEW DYNAMIC LIGHT- VALVE

395

actual practice to ascertain the best possible approximation by two
straight lines. It is evident that the discrepancies between the
straight lines and the theoretical curve can not at all points show equal
influence upon the frequency curve. When the damping plate is at
some distance from the ribbons, small alterations of the distance are
practically insignificant. Beyond a certain distance it would make
no difference even whether the plate were in place or not. It is there-
fore necessary to have some idea of the errors caused by discrepancies
from the ideal curve. For this reason measurements as shown in
Fig. 5 were made. At fixed frequency, constant temperature, and
constant distance of the lens, the amplitudes are measured with rela-
tion to the distance of the damping plate. The resulting curve

FIG. 7. Cross-section through casing.

shows plainly at what distance of the plate the amplitudes reached
the rated value and at what distances errors of amplitude reached
values of =±=0.5 db., =±=1.0 db., etc. The readings can be laid out as
a set of curves as shown in Fig. 6. Here the curve shown in full line
indicates the respective distances of the damping plate for an assumed
case in which at all temperatures the rated value of the amplitude is
reached exactly. Curves shown in dotted lines indicate the distance
at which discrepancies from the rated value reach =±=0.5 db. and =±=1.0
db. Of course, the discrepancies apply only to the upper end of the
frequency curve of the light-control instrument. If for this range a
tolerance of =±=1.0 db. is permissible, then all that is needed is so to
place the two straight lines 2 and 3 (Fig. 3) in the zone indicated by
the two extreme curves that at no point of the temperature interval
is the zone exceeded. After entering the straight line in its correct
position on the sketch it becomes evident at what temperature fe

396

E. GERLACH

(Fig. 3 ) the adjusting screw 9 (Fig. 2) should make contact. The
exact angle of inclination of the two straight lines can be read off the
chart, and there is no difficulty in determining the correct dimen-
sions of the bimetallic spring if the constant of the material is known.
Fig. 7 is a cross-section through the casing. The permanent mag-
net is circular in shape, with two poles diametrically opposite each
other. The upper cover is soldered to the casing after all final adjust-
ments have been made. Strong connecting screws are mounted on
the cover. Soldered connections are provided for the lead-wires
between the terminals of the ribbons and the connecting screws on the
cover, after the latter has been put in place. To make this possible
the wires in question are led through in such a way as to protrude
slightly through the oil inlet opening (not visible in Fig. 7) of the

FIG. 8. Limiting frequency curves for
the temperature range +1° to +35°:
ordinates, amplitude; abscissas, frequency.

cover, and can readily be soldered with the cover in place before
closing the opening with a screw cap.

Fig. 8 shows two frequency curves of the apparatus. Within
these limiting curves are located the frequency curves between +1°
and +36° C.

DISCUSSION

MR. FRAYNE : What is the length of the bridge between points 2 and 4 on
Fig. 1 ? What are the tension of the ribbons and the strength of the magnetic
field?

MR. LICHTE: The length of the ribbons is about four millimeters, the strength
of the magnetic field about eight thousand gauss. I do not know exactly the
tension of the spring.

MR. ALBERSHEIM: What is the maximum angle through which the mirror
turns?

MR. LICHTE: About one degree.

COLOR STILLS*
O. O. CECCARINI**

Summary. — Color photography applied to publicity stills represents a very valuable
asset for the motion picture industry. The demand for high-quality results and speeds
places color stills in a special class of their own, and therefore the discussion of the
various methods of obtaining color -separation negatives is carried out essentially
upon the basis of these requirements. For the production of sample prints on paper,
many of the available methods are discussed, such as carbon, carbro, dye transfer,
chemical toning, etc., emphasis being placed upon the methods that are capable of
giving results most suitable to the needs of motion picture industry. The general dis-
cussion and the extensive bibliography should be found valuable by those who wish to
study the subject of color photography in greater detail.

The increased interest and public appreciation of color photography
during the last few years can very probably be attributed to the ex-
cellent results attained with various color processes, which in turn
have been made possible by the improvement of the photographic
materials available. While no principles have been discovered that
were not known twenty or forty years ago, in those days the com-
paratively low speed of the panchromatic material and the limited
variety available made impossible the realization of ideals, except in
the case of a few experts who willingly sacrificed their time in order to
produce something different.

Color photography, as applied to publicity color stills, represents
a very valuable asset for the motion picture industry. While the
methods of arriving at acceptable results are many, the requirements
of this industry can be regarded as in a special class by themselves.
The following discussion of the most popular color processes is there-
fore carried out essentially on the basis of these requirements.

The literature of color photography is very extensive and very
complete. Those who wish to begin with the fundamentals will find
many text-books listed in the attached bibliography. The manufac-
turers of photographic material are also issuing complete and detailed
information of the uses of their products, and it will be found today

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received June
30, 1937.

** Consulting Engineer, Metro-Goldwyn-Mayer Studios, Culver City, Calif.

397

398 0. 0. CECCARINI [J. S. M. P. E.

rather a simple matter for anyone who cares to follow the instructions
carefully, to produce acceptable color prints on paper.

We shall begin with a brief description of the methods for producing
color-separation negatives. The oldest known method is that of
making three separate negatives in an ordinary camera, in succession,
each with its corresponding color-separation filter.

Next in line is the so-called "sliding or repeating back" which can
be readily attached to any ordinary camera. This back carries the
three color-separation filters, and a plate holder for a single long
plate, or three separate plate holders adjacent to each other and upon
which the exposures afre made. The operation consists in sliding
back the required amount after each exposure, by hand or by means
of an antinous release. Some time ago an automatic repeating
back was introduced in England by the Color Photographs, Ltd.,
operated by clockwork, which performs all the operations automa-
tically in a rather short period of time — about two seconds, or slightly
less.1

Obviously the use of separate plate holders in an ordinary camera,
or of the usual repeating back, are applicable only to still-life subjects,
but not very applicable to portraits. The automatic repeating back
can be used satisfactorily for portraits in studios.

Color-separation negatives, particularly for portraits, can be ob-
tained also by means of the so-called color-screen plates, or color-
screen films such as the Lumiere and Agfa color plates, Lumiere
Filmcolor, and Finlay color plates, and the Dufaycolor film. The
Lumiere. Agfa, and Dufay materials contain the color-filter elements
in minute, irregular or regular geometrical patterns, these color ele-
ments acting as taking filters as well as projection filters, after the
reversal process. The Finlay plate uses as a taking filter a plate of
geometrical pattern physically separate from the negative emulsion.
Descriptions and uses of the color-screen plates and films can be ob-
tained from the manufacturers of these materials.

For reproduction work, or for producing color prints on paper by
means of the original color-screen plate or film, it is necessary to
produce color-separation negatives from the screen-plate or film.
This is ordinarily accomplished by copying the original color-screen
plate through three-color separation filters of very narrow trans-
mission. The Finlay color plate is different in this respect, as color-
separation negatives can be obtained from the Finlay positive by
means of the so-called block-out screen. Although acceptable re-

Oct., 1937] COLOR STILLS 399

suits are possible by means of the color-screen method, the quality,
however, is not comparable with that of the method of making color-
separation negatives directly on three separate panchromatic emul-
sions. The reasons are many but very probably the major one is the
undeniably narrow range of sensitivity (latitude) of the emulsion of
the color-screen plate or film. The Kodachrome film now available
in 35-mm. and substandard sizes, but which will be available shortly
as cut film, promises to be a medium vastly superior to the present
color-screen material chiefly because of its continuous tone character,
its high color-sensitivity and wide latitude. In the same class can
be placed the new Agfacolor film recently announced.

During the past few years Duf aycolor film has achieved great
popularity due particularly to its increased speed, and also to the
fact that its geometrical color-screen is extremely small and permits
a certain degree of enlargement before the pattern becomes visible to
the naked eye. It is a comparatively simple matter to carry through
the various chemical operations and produce interesting color trans-
parencies. Motion picture studios make considerable use of the
Dufaycolor film by supplying it in the form of transparencies to pub-
lishers, who, in turn, produce their own color-separation negatives
for printing purposes in magazines, weekly periodicals, and news-
papers.

Whenever high-speed and high-quality work is desired in motion
picture studios, the color-separation negatives are made today by the
so-called "one-shot" camera, of which several models in various
sizes are available in the open market. This type of camera consists
essentially of two partially reflecting mirrors disposed at convenient
angles by means of which the cone of the light emitted by the lens is
divided into three different components, each of which is directed to
the appropriate filter and plate. It can be roughly assumed that
about one-fourth of the light passing through the lens reaches each
color-separation plate, since the partial reflecting mirrors cause a cer-
tain loss of light. Taking an average filter-factor of five we can say
that approximately one-twentieth of the light passing through the
lens can effectively be directed onto each negative. A slight increase
in overall speed can be attained by using for the blue-separation nega-
tive a fast color-blind emulsion, and, therefore, employing a highly
transparent first mirror, thus directing the bulk of the light to the
second mirror, which divides it into suitable proportions for the
green- and red-separation negatives. The use of two different nega-

400 O. O. CECCARINI [J. S. M. p. E.

tive emulsions required by this method is sometimes open to objec-
tions.

It is universally accepted that the properly designed "one-shot"
camera is the most useful and fool-proof instrument available today
for producing color-separation negatives. Not only are three color-
separation negatives of identical size obtained, but in each case the
full range of the panchromatic emulsion is made use of for each nega-
tive. In addition, if any slight movement or diffusion occurs in the
background, or the foreground, it appears identically in all the three
negatives, so that when superimposing the three constituent color
positives, no color fringes are noticeable as happens sometimes with
repeating backs. This type of camera, due to its complicated con-
struction is usually very expensive, but as the primary cost of equip-
ment used in the motion picture industry is of secondary importance
to the quality of results desired, it can be completely discounted.
This camera is available today in various forms, each inventor having
attempted to minimize certain imperfections or disadvantages in
favor of the others. Therefore, in this respect we find that personal
opinion has played a great part in the arrangement of the mirrors
and the geometrical outline. The design of the typical "one-shot"
camera also dates back many years. A very interesting and com-
plete description of the various forms of optical combinations sug-
gested in the past can be found in Wall's History of Color Photography.

It must be emphasized at this time that the following critical
considerations about "one-shot" color cameras represent the personal
opinion of the writer, and may be very much at variance with the
opinions of other color workers. As already stated, we are at this
moment considering the subject as applied to color portraiture for
the motion picture industry.

When choosing a "one-shot" color camera, several considerations
must be given particular attention. In the first place, we are com-
pelled to judge of very little value those types of cameras in which
splitting the light-cone is accomplished by dividing the exit pupil
of the lens into three different zones. This construction gives rise to
the so-called "parallax," and only objects in the focal plane of the
lens will superimpose correctly, but anything beyond, or near, will
be displaced in opposite directions in the three negatives and will
therefore produce color fringes. In addition, this particular design
suffers greatly from unevenness of illumination throughout the area
of the plate, so as to cause a predominance of one color on one side of

Oct., 1937]

COLOR STILLS

401

the finished picture, and of the other colors on the opposite side.
Cameras of this type have been in use in the past, and some are still
available today. Although it is conceivable to think of subjects, por-
traits, for instance, with a uniform background devoid of any pattern,
we must admit that the field of application is extremely limited,
because we are seldom at liberty to choose a background suitable for
this type of camera. Experience and theoretical considerations have
shown that a satisfactory image can be attained only by allowing each
plate to encompass the full cone of light emitted by the lens. On the

FIG. 1. "One-shot" color camera
using crossed partial mirrors.

//

FIG. 2. "One - shot" color
camera with partial mirrors dis-
closed one after another at an
angle with the central axis.

basis of these considerations we find the satisfactory "one-shot"
color camera restricted to essentially two types :

CO The type that involves crossed partial mirrors (Fig. 1.).

(2) The type that has the partial mirrors disposed one after another at an
angle with the central axis. The two mirrors may be parallel to each other, or at
opposite angles. (Figs. 2, 3, and 4.)

With regard to the last type, again we find cameras in which the
first mirror toward the lens is placed at an angle of approximately
45 degrees and others in which the same mirror is placed at an angle
much smaller than 45 degrees. The deviation in the set-up is brought
about by two major considerations. If the mirror is placed at 45
degrees, the general appearance of the camera is a little more pleasing
than if the mirror is placed at an angle of, say, 30 or 35 degrees. If
the mirror is placed at 45 degrees or very nearly so, it can be readily
proved geometrically that the light scattered by the color-filter inter-

402

O. O. CECCARINI

[J. S. M. P. E

cepting the light from the first mirror is not directed toward the plate
that intercepts the image formed by the second mirror. Therefore,
the least fogging effect can be expected from this particular arrange-
ment, and much less than if the mirror were at an angle of 30 or 35
degrees. On the other hand, a mirror placed at 45 degrees does not
give as uniform a reflection as if the angle were smaller. This point
can be readily appreciated by computing the reflection of the bound-
ary rays striking the mirror by means of the Fresnel formula :

R = -

rsin* (i - r) ton2 (i - r)"|
Ltn* (i + r) tan2 (i + r)J

where i and r are the angles of incidence and refraction.

This difference in coefficient of reflection for different angles is

FIG. 3. Mirrors at opposite angles.

FIG. 4. Mirrors parallel.

appreciably modified by the partial coating of the mirror. Never-
theless, it is there to an extent that might, in the opinion of some
workers, be deemed objectionable. Manufacturers who prefer to
place the first mirror at angles smaller than 45 degrees contend that
the light scattered by the glass surface on the filter will be again re-
flected partially by the same mirror toward the lens, and only an
extremely small percentage will reach the second plate and be entirely
out of focus. The extremely small amount of fog that might be
produced would be uniformly distributed throughout the plate and
would not impair the quality of the image. Therefore, the uniformity
of distribution of the light would appear as a more important require-
ment.

The second mirror is invariably placed at an angle smaller than 45
degrees, as the light scattered by the filter of the second plate does
not ordinarily strike the back plate.

Oct., 1937]' COLOR STILLS 403

The type of camera with crossed mirrors has the chief advantage of
permitting the use of lenses of short focal-length, which might be
regarded as convenient for outdoor or landscape work. However,
due to the form of construction, one of the mirrors in the camera is
solid throughout, and the other one is split into two co-planar sec-
tions, the joining point constituting a small vertical zone that inter-
cepts the light from the lens. The joining line ordinarily does not
constitute an objection except when the lens is stopped down to a
very small value, in which case it might begin to cast a shadow in the
middle of all the three plates. This ordinarily occurs at a stop be-
yond/716.

As to the nature of the partial mirror, glass has been used by many
manufacturers, while others prefer pellicular mirrors. Glass partial
mirrors might give rise to double images, caused by the back surface
of the mirror when the coefficient of reflection of the front surface is
appreciably less than fifty per cent. The pellicular mirrors do not
give rise to secondary images because they are extremely thin and
the back image coincides with the front image. In the case of glass,
however, the back image can be minimized in several ways. In the
first place, we can use glass of low index of refraction ; or, we can use
a softer glass of higher index of refraction and minimize the secondary
image by changing the index of refraction of the back surface by
evaporating onto the surface a transparent substance of low index,
such as fluorite.2 Another method consists of changing the index of
refraction of the glass by a chemical treatment which in itself is
nothing else but a microscopic etching of the glass.3 Several chemical
substances are known to produce this effect. If such procedure is
decided upon the glass is first treated chemically so as to change the
index at the surface boundary, after which the reflecting metal is
evaporated or sputtered. The back surface reflection coefficient can
be readily evaluated in terms of the index of refraction by means of
the Fresnel formula given above. For comparing the behavior of
two types of glass we can assume that the light ray is normal to the
surface of the glass, in which case the formula becomes

D ^

where n is the index of the glass.

If the index of one glass is, for instance, n = 1.55, then R = 4.05
per cent: while if the index is. say, 1.44, then R = 3.24 per cent.

404 O. O. CECCARINI [J.'s. M. P. E.

Thus we see that a small change in the index of the glass produces a
correspondingly large change in the coefficient of reflection.

Unquestionably, glass partial mirrors are always far more per-
manent and dependable than pellicular mirrors, although with care-
ful attention in handling, the latter type should also be found quite
satisfactory.

Glass partial mirrors introduce a slight distortion of the images due
to refraction of the glass. However, when the thickness of the glass
mirrors is not in excess of 0.050 inch, then the only correction usually
necessary is readily obtained by tilting the plate receiving the image
reflected by the second mirror. The through image is sufficiently
compensated by the two mirrors, placed at opposite angles.

For the surface treatment of mirrors, whether they be glass or pellicu-
lar, several metals have been successfully used. Gold, for instance, re-
flects a large percentage of orange-red light and transmits quite freely
a blue-green light, and its efficiency becomes quite satisfactory in this
respect by carefully choosing the sequence of the color-filters. The
most efficient metal is silver, but since it readily tarnishes when ex-
posed to air, it is necessary to protect it with some kind of lacquer,
which unfortunately, unless very carefully applied, may change the
optical quality of the surface. For that reason it has been found
lately more practicable to use aluminum, which can be applied by
evaporation in high vacuum; or a combination of aluminum and
chromium, which adds durability; or chromium alone. Next to
silver, aluminum is the most efficient and is quite stable. It has been
found that aluminum-coated mirrors change very rapidly during the
first few hours after treatment, and gradually become permanent as
the transparent aluminum oxide forms and protects the remaining
aluminum from being further oxidized in the presence of the air.
Very probably the combination of aluminum and chromium can be
regarded as the most satisfactory from the standpoint of hardness and
general durability, although not quite as efficient as aluminum alone.
In general, the efficiency of a partially aluminized mirror is of the order
of 80 to 85 per cent.

Partial reflecting mirrors made of glass can be further improved
with respect to the secondary image by using glass colored in the
mass. For instance, if the blue-separation negative is to be formed
by the first mirror, we should use for this mirror a yellow-colored
glass that would produce a secondary image of yellow color, which,
in turn, would be absorbed by the blue filter in front of the negative.

Oct., 1937]

COLOR STILLS

405

Similarly, if the reflection from the second mirror is to be used for the
green-separation negative, we should use for the second mirror a red-
colored glass, thereby producing a red secondary image, which would
be absorbed by the green filter. This expedient of using colored glass
is especially desirable when the percentage of reflection of each
mirror is appreciably less than fifty per cent. In general, it is more
expedient to reduce the secondary image by using a glass of low
index, or by chemically treating the glass surface as previously indi-
cated.

Another form of "one-shot" camera, not quite as expensive as the
double mirror type, is one involving a single partial reflecting mirror
(Fig. 5), and in which two of the three color-separation negatives are
exposed face to face in the form of a
bipack. Several arrangements can
be made. For instance, the bipack
can be made to record the green and
the red sensation by exposing the bi-
pack through a yellow filter and re-
cording the blue sensation on a sepa-
rate negative. For the blue-sensation
negative we are then at liberty to use
a panchromatic material in connec-
tion with the blue filter, or we can
use an ordinary color-blind material
of suitable sensitivity. An alterna-
tive arrangement would be to record
the blue and the red with the bipack by exposing through a minus
green or magenta filter, and then obtain the green-separation nega-
tive on an orthochromatic or panchromatic material through the
regular green filter. Whatever arrangement is used, the ratio of re-
flection to the transmitted light of the mirror is to be arrived at by
considering the relative speed of the bipack with its proper filter and
the negative material chosen for the third negative. Manufacturers
of bipack material give detailed information and usually supply the
third film to be worked in connection with the bipack.

The chief drawback of the single-mirror "one-shot" camera is with
respect to the blue printer or red-separation negative. Since this
negative (the second of the bipack) is appreciably diffused due to the
scattering of light by front emulsion, the net result is a soft blue
positive which might be considered undesirable with some subjects.

FIG. 5. "One-shot" camera in-
volving a single partial reflecting
mirror.

406 O. O. CECCARINI [J. S. M. p. E

It must be remembered that the blue printing color is the one that
contributes most to the definition. With suitable pressure in a plate-
holder carrying the bipack, this softness of the blue printer negative
can be appreciably minimized. Nevertheless, the peculiarity al-
ways remains, and from that standpoint this method of making color-
separation negatives can not be regarded as being ideal, although
quite satisfactory results can be attained. As mentioned before, the
initial cost of a high-grade three-color separation camera is quite
secondary when considered from the standpoint of its application
to the motion picture industry and, therefore, the double-mirror kind
should be given preference to any other type.

Having at our disposal a suitable color-separation camera, we shall
proceed to determine the necessary requirements for obtaining a set
of color-separation negatives of the proper quality for reproduction
purposes.

Exposure can be made with ordinary daylight, with flashlight, or
with incandescent or photoflood lights ; but in no case should the lights
be mixed, as falsification of color will invariably result. The manu-
facturers of color cameras ordinarily supply sets of filters or com-
pensation filters for use with the various kinds of illuminants.

The theory of tone reproduction demands that the exposure of the
negative material be confined within the straight-line range of the
material. It is also necessary that the three negatives be developed
to the same contrast, although slight variations are always permis-
sible. If the same panchromatic material is used for all three nega-
tives, it will be found that the blue-filter negative always shows a
much lower contrast than either the green- or red-filter negatives, for
the same time of development. Therefore, this 'particular negative
must be developed for an appreciably longer time, which must be
determined in practice by the regular sensitometric procedure. The
red- and green-filter negatives are sufficiently close together, and do
not usually require any correction. Information about the proper
development can also be readily obtained from the manufacturers of
the photographic negative material that is being used.

Practice has also shown the desirability of including in the subject
a so-called neutral-gray wedge. By means of the neutral wedge, we
can determine whether the three negatives are uniformly exposed and
developed to the same contrast. Furthermore, by its use we can
determine with extreme accuracy the printing ratio. It is seldom
possible to obtain three accurately balanced negatives requiring the

Oct , 19.37] COLOR STILLS 407

same printing light, and therefore the measurement of the transmis-
sion value of the corresponding steps of the gray wedge will obviate
many trial printing exposures afterward. In this connection a
very valuable instrument for the color worker is a transmission
densitometer now commercially obtainable from the Eastman Kodak
Company. The same densitometer can al^o be obtained in a form
that permits measurement of the reflection from paper surfaces so
that further check of the exposure of the gray wedge on paper may be
made after printing. This, of course, applies to those color printing
methods that require the use of bromide positives as intermediate
steps.

Another important point to be kept in mind in color photography
is to avoid extreme light contrast, for several reasons. If, for in-
stance, we should wish to cover the full range represented by the
scale of the negative material, it would be necessary that the three
negatives be extremely accurately exposed, otherwise color tones at
the extreme ends of the scale would depart appreciably from the true
values. This is readily understood when we consider that the
characteristic of the photographic material consists essentially of
three regions: (a) the straight-line portion, which is the useful por-
tion, and in which a linear relation exists between the light value of
the subject and the light value of the photographic reproduction;
(6) the underexposure region ; and (c) overexposure region, in which
no linear relation exists. If the light range of the subjects is moderate
and covers only a part of the straight-line region, it is also obvious
that the three negatives can depart slightly from each other in the
value of the gray wedge, and the only adjustment necessary for correct
tone reproduction will be a proper change of printing light. If, on
the other hand, the light range is very great and the negatives are
out of balance with respect to the gray wedge, we shall find that some
of the color tones in some of the negatives will be in the region of
overexposure, and in the other negatives in the region of under-
exposure. Adjustment of the printing light under those conditions
will not permit acceptable color reproduction, and we can hope to
obtain only a fair reproduction of the middle tones.

Only after considerable experience in the production of color-
separation negatives and in printing methods can one attempt to
extend the light range.4'5

It must be also kept in mind that if color photographs are to be
reproduced by photomechanical printing processes, the light range

408 O. O. CECCARINI [J. S. M. P. E.

available with the usual printing inks is appreciably less than the
range attainable with bromide and carbon prints. For instance, a
platinum paper might have a light range of 80 to 1, while the range
of printing inks is well known to be a fraction of that. It would be
therefore impracticable to attempt to reproduce a subject with ex-
cessive light contrast.

Having obtained a correct set of the color-separation negatives
with the gray wedge included, and assuming that the contrast of the
three negatives is also uniform and within practical values, we are
required to produce a color proof on paper. For this purpose several
methods are available. We might use the method of three super-
imposed carbon prints ; we might use the method involving the trans-
fer of transparent aniline dyes; we might produce the three constitu-
ent images by chemical toning methods to be afterward super-
imposed on paper; or we might combine some of these methods to-
gether.

Today, unquestionably, the color print made by a carbon process
is the most beautiful and the most permanent, but it is also probably
the most difficult to make. However, in view of the exceptional re-
sults that can be obtained by it, a description of it will be given,
although information can be obtained from the makers of the carbon
tissues,6 and from many text-books listed in the attached bibliography.
The carbon prints can be produced in two ways : We can make them
by the method of enlarged negatives to be printed afterward by con-
tact upon carbon tissues of appropriate colors, sensitized in a mixture
of bicromate of potassium or ammonium ; or we might adopt the more
modern method of making enlargements upon suitable bromide papers
and then allowing a chemical reaction to take place between the bro-
mide paper and the carbon tissue, after the tissue is suitably sensitized
in chemical baths containing bleaching and hardening agents. The
latter method is commonly known as Carbro method. Since the
procedure is identical in the two methods after the tissues have been
reacted upon by the exposing light through the negative or by the
tanning action of the bleaching and hardening agents, we shall ex-
amine the Carbro method only.

From the three-color separation negatives three bromides, either
by contact or enlargement, are made with an exposure in accordance
with the transmission readings of the gray wedge, care being exer-
cised that during the enlarging the size is- accurately maintained.
Unless one is absolutely sure of the uniformity of the illumination of

Oct., 1937] COLOR STILLS 400

the projection apparatus, the negatives must be placed in identical
position in the negative carrier so that any lack of uniformity of light
will affect all three negatives to the same degree. The most suitable
bromide paper for this work is one having a soft or unhardened emul-
sion and must be rich in silver content. Suppliers of carbon tissues
list the most convenient types of bromide papers, and since different
papers require variations in technic and manipulation, one should
endeavor to specialize in one type only. This can not be regarded as
a limitation because the bromide paper serves only as an intermediate
step, and the degree of control available in the form of bromide de-
velopment and the compounding of sensitizing solutions for the tissues
will be found ample for requirements demanded by negatives of
average quality. The quality of bromide print should be of the
highest value, without fogging of the highlights and without exces-
sively deep shadows. It is also very important to develop the three
bromides to the same contrast, and in order to facilitate this step it
is desirable to use a large quantity of developer if the prints are
made in succession, or to develop each bromide separately in a small
quantity of fresh developer. In any case, the temperature of the
developer should be kept the same because the activity of the
developer is materially affected by its temperature.

With regard to the fixing bath, although many persons recommend
plain hypo rendered acid with sodium bisulfite, or potassium meta-
bisulfite, the writer has found that the use of a plain hypo without
any acid is ordinarily to be preferred unless one is willing to pay ex-
treme attention to the degree of washing that has to follow. Any
acidity of the emulsion of the paper affects the behavior of the Carbro
solution to a very marked degree. It is, therefore, desirable to avoid
the acid and discard the hypo after the bromides have been properly
fixed. The condition of the wash water might also affect the behavior
of the Carbro solutions, particularly if lime or other chemical sub-
stances are present to an appreciable extent. Many Carbro workers
treat the bromide prints in a solution of diluted acetic acid (half
ounce glacial acetic acid in twenty-five ounces water) for about three
or four minutes followed by eight or ten minutes of wash of running
water. The writer finds that under these conditions the amount of
acetic acid retained by the bromides is too great and the Carbros thin.
A better procedure is to use a much smaller amount of acid, l/4 per
cent solution of acetic acid, for instance, for exactly four minutes
followed by a wash of running water again for four minutes, after

410 O. O. CECCARINI [J.S. M. P. K.

which the bromide papers can be slightly drained and placed in a tray
with a small amount of distilled water until used.

It will be found that if this procedure is followed, the quality of
the Carbro image will be of normal strength, as if no acid bath had been
used, and with none of the highlight irregularities and defects caused
by chemical impurities of the wash water.

The Carbro solutions ordinarily consist of bleaching agents as a first
bath and controlling agents as a second bath. The compounding and
use of the two baths are amply described in the pamphlet on trichrome
Carbro printing by the makers of carbon tissues. The writer again
finds it more expedient and convenient to use the combined or single
bath procedure. The single-bath method permits much more even
results, and it is not as critical with respect to time as the two-solution
method. With the two-solution method the time of immersion in the
second bath controls the degree of contrast of the resulting print,
while with the combined or single bath the variation of time of im-
mersion has very little effect upon contrast. This can hardly be
called an objection, as all the bromides are supposed to be of equal
contrast and suitable quality. A change of contrast, however, can
be readily attained by first compounding the normal bath for the
tissue or tissues requiring normal contrast, then adding to the bath
a small amount of controlling solution for the other tissue or tissues
requiring less contrast. In other words, the procedure is to leave
for last the tissue that must be made softer, because a chemical con-
trolling agent can be added to, but not subtracted from the bath.

In order properly to produce a desired change of contrast the worker
must know the quality of contrast attainable with definite quantities
of controlling agents. This is readily determined by making several
identical graded strips on the bromide paper, and then treating a
black tissue with the single bath of different composition, a record
of which must be carefully kept. Upon developing these various
tissues a measurement of the resulting contrast can be readily made
by means of the reflection densitometer. It is also possible to ex-
press in a tabulated form or graphically, the variation of contrast
in terms of the controlling agents present in the single bath, so that
in future any desired variation of contrast can be readily interpolated
from the record on hand. If a reflection densitometer is not available
for measuring the graded carbon strips, the transmission densitometer
can be used for the purpose by developing the graded carbon strip
on thin transparent celluloid. If this procedure is adopted one must

Oct., 1937] COLOR STILLS 411

bear in mind that the apparent contrast of -a graded strip by trans-
mitted light is approximately one-half its value by reflected light.
For a more accurate relation between transmission and reflection
densities one might refer to an article by F. F. Renwick in the Photo-
graphic Journal (Jan., 1937).

The writer finds also that except in the case of prints smaller than
8 by 10 inches, the use of an automatic squeegee to produce intimate
and uniform contact between the bromide and the carbon tissue is of
extreme importance. Such squeegees are not ordinarily available
commercially, but can be readily assembled by anyone and do not
present any great difficulty. However, the required roller pressure
must be adjustable, and a few experiments are necessary before the
right degree of pressure is arrived at. It will be found, ordinarily,
that too much pressure will tend to produce irregular patches and the
pressure must be gradually reduced until any trace of irregularity is
unnoticeable. A critical test for the pressure can be readily carried
out by exposing a bromide paper very lightly and uniformly, and
using the blue carbon tissue for tests, as with this color any irregu-
larities throughout the surface that would readily pass unnoticed with
red and yellow tissues are immediately noticeable. In this respect it
will be found that the single-bath method is less critical to the
squeegee pressure.

It will also be found that the use of a combined or single-bath has
been recommended in two different ways. One method consists of a
preliminary bathing of the tissue in plain water, while the other
consists in placing the tissue in the sensitizing bath without pre-
liminary treatment. The latter method is to be preferred from the
standpoint of evenness in connection with the automatic squeegee.

The next printing process that has attained considerable popularity
during the last year or two is the relief or imbibition process. This
process is exemplified by the Eastman wash-off relief, and the very
complete and accurate instructions issued by the Eastman Kodak
Company make it possible to produce very acceptable prints on paper
with a relatively moderate background of experience.7 The sequence
of the various operations is very carefully outlined in the instructions,
and unless one departs deliberately from the instructions there is very
little chance of going wrong. There is, therefore, very little that one
can add to it.

The color prints made by this method consist of extremely trans-
parent dyes, and the results are therefore very luminous. They lack,

412 O. O. CECCARINI [J. S. M. P. E.

however, the peculiar sensation of depth that is characteristic of
the prints made by the Carbro process. Since acid dyes are used for
the process the color prints are also undoubtedly quite permanent,
although perhaps not as much so as Carbro prints.

Instead of using the Eastman wash-off relief film one could also use
a special carbon tissue for the purpose of producing the relief image
to be subsequently used as a matrix. When this carbon tissue is
used for the purpose, the process assumes the trade name of Dyebro,
material for which is manufactured by the Autotype Company in
England.

Obviously, in order to produce the matrices by means of the carbon
tissue one must make bromide prints as the first step by substantially
the same procedure as described previously for Carbro. An alter-
native variation of the Dyebro process consists in toning chemically
the bromide print obtained from a red-filter negative by means of an
iron blue toner, and subsequently transferring on to this toned bro-
mide the magenta and the yellow color by means of the carbon tissue
matrices.

In carrying out the process in this form one has to contend with the
proper determination of the effective contrast of the toned blue image
with respect to the effective contrast of the magenta and yellow dye
images transferred on to it. The correct values of the contrast must
be arrived at empirically. It is also necessary to determine empiri-
cally the law of contrast variation for the three images in order to be
able to make the required changes if necessity for changing the con-
trast should arise. From the standpoint of simplicity and uniformity
the wash-off relief film supplied by the Eastman Kodak Company is
certainly preferable.

While the cost and the time required to produce the color print by
the wash-off relief or imbibition method is approximately the same as
by the Carbro method, additional prints of the same subject can be
readily made by the imbibition process in a relatively short time.
The only time required is the time necessary for the matrices to absorb
the dye, and the time necessary for transferring it on paper, as these
matrices can be used repeatedly for a very large number of prints.
In the case of Carbro, of course, the time is the same for each print.
With proper precautions the images obtained by dye transfer can be
made to retain a sufficient degree of sharpness.

The recent introduction of the complete toning process for the three
constituent images under the trade-name of Chromatone8 makes it

Oct., 1937] COLOR STILLS 413

possible to attain colored images of a degree of sharpness strictly
identical with that of a bromide print. The Chromatone process is
also fully covered by careful instructions issued by the manufacturers,
and by this method also it is possible to attain very satisfactory color
prints on paper with no other knowledge than the ordinary photo-
graphic experience that anyone can readily acquire. The constituent
colors of the Chromatone process are also fairly close to the ideal com-
plementary colors and, therefore, satisfactory color-balance and
intermediate tones are readily obtainable.

The three-toned images consist of a regular gelatin emulsion sup-
ported on thin layers of collodion. The chief difficulty with the col-
lodion support is that when it is mounted upon the final paper support
and dried it tends to curl inward, and must be carefully mounted.
Also, the glossy appearance of the collodion surface might not be as
artistic as an ordinary gelatin surface. In this case, however, it is
possible to assemble the images with the gelatin surface uppermost,
which, of course, requires that the printing be done through reversed
negatives. The blue and magenta images obtained by chemical
toning are not very transparent, and the resulting prints are therefore
not as brilliant as prints made by the imbibition method or by the
Carbro process. Nevertheless, all in all, the Chromatone method can
be considered quite a satisfactory procedure to produce quick proofs
from color-separation negatives. The time required for making each
print by this process is also approximately the same as for the Carbro
and imbibition methods, and, as with the Carbro, the same time is
required for each successive print, so that if several prints are required
the imbibition method is again to be preferred. Very little is known
about the permanency of the Chromatone images.

Another process that is very little practiced, but which is never-
theless capable of excellent results, consists in making prints on posi-
tive films and then treating the positives by some of the well known
mordanting processes. The copper mordant is usually the most re-
liable. The dyes to be used with the mordant process are obviously
basic dyes, which unfortunately are not as fast to light as acid dyes
and, therefore, color prints made by this method should not be unduly
exposed to sunlight. Assembling the mordanted images can be car-
ried out by the method suggested by Namias many years back,9
which consists in cementing the yellow positive to a final paper sup-
port, and, when dry, removing the celluloid base of the film by dis-
solving it in acetone, thus leaving only the original gelatin emulsion

414 O. O. CECCARINI [J. S. M. P. E.

formerly carried by the film base. The red image is applied next,
also preferably with a gelatin cement, and when dry the celluloid
support also is removed by treatment with acetone. The blue posi-
tive is assembled in a similar manner. In this way the three-color
positives are assembled with only the gelatin layers between them,
and the quality and sharpness of color images attainable by this
method are indeed surprising. The time required for producing the
complete picture is comparable with that of the processes so far
described.

It is possible to obtain extremely brilliant dye mordant images also
by transferring the basic dyes to a final support coated with collodion
emulsion, since collodion has a great affinity for basic dyes. This
method was suggested by R. von Arx.10 The same author suggested
also transferring mordanted dyes to a final support containing a
mordant of a more powerful nature than the one by which the dye
images are made.

There are other processes in commercial use today and which to
some extent are closely related to those already described. Among
them might be mentioned the Duxochrome process. This process
resembles very much the Deck's color-sheet process, which was intro-
duced commercially about 1923 and exploited by the American Raylo
Corporation. These sheets carry in suspension in the gelatin layer
the necessary dyes, together with the silver bromide emulsion. The
exposure of the sheets is carried out as with ordinary enlarging paper,
and after development by means of a tanning developer, the gelatin
emulsion is washed off in the hot water, thus producing a relief gela-
tin image. After the developed silver images are bleached the re-
maining colored images in relief are transferred to a gelatin-coated
final support.11 This method is possibly slightly speedier than any of
the methods so far described, but the cost of the material is appreciably
higher, and the quality of the image does not surpass that attainable
with the Carbro process, although it might be less difficult from the
technical standpoint.

The color technician of a motion picture studio is seldom required
to produce more than one proof on paper, and it is therefore very
difficult to suggest the most appropriate means for producing this
proof, as the time involved for a single print is substantially the same
for nearly all the processes mentioned so far. In choosing a method,
one therefore must be guided by the precision and the standard of
quality demanded, and by the ability of the personnel who have to

Oct., 1937] COLOR STILLS 415

carry through the actual manual operations. It is conceivable, how-
ever, that cases may exist for which a fairly large number of prints of
the same subject might be desirable; several dozen, for instance, or a
few hundred. In such case to produce the prints by the chemical
processes so far described is out of the question, and the initial cost
demanded by setting up printing matrices by any one of the photo-
mechanical processes is unreasonably high. In such cases it seems
that the Collotype method might be rightfully called into play.12

This method, although substantially a photomechanical process, is
very closely related to the Bromoil13 process used by many pictorial-
ists. The production of Collotype printing plates is substantially
an easy matter, and suitable film can be readily obtained commercially
today. Since this method relies upon the property of the bichro-
mated gelatin to reticulate when differentially hardened by ex-
posure to light and subsequently treated with a mixture of water and
glycerin, the resulting images are extremely beautiful and delicate
in details, and resemble very closely the quality of a photographic
print. Color reproductions by this method are extremely beautiful,
and it is possible to obtain as many as a thousand pulls from each set
of Collotype plates. The method could, therefore, be readily sug-
gested for the production of portraits of outstanding personalities,
or prints for lobby displays, or in any case where the demand does
not exceed a few hundred samples.

It is conceivable also that the allied Bromoil process could be used
instead of Collotype for a limited number of prints (a dozen, for
instance), in which case, however, the matrices should be inked by a
mechanically operated automatic brush in order to produce a rapid
and uniform inking. The general control is done strictly by the
moisture content of the gelatin. The use of a bromide paper specially
manufactured for Bromoil is not necessary, but, instead, a regular
positive film can be very conveniently employed. The film has the
advantage of retaining its size and permitting accurate registration.

REFERENCES

1 "Repeating Back for Color Exposures," Brit. J. Phot. Color Supp., 79,
(June 3, 1932), p. 22.

2 STRONG, J.: "On a Method of Decreasing the Reflection from Non-Metallic
Substances," /. Opt. Soc. Amer., 26 (Jan., 1936), p. 73.

3 U. S. Ordnance Department Document No. 2037, p. 77.

4 POTTER, R. S. : "Methods of Making Three-Color Separation Negatives,"
Defender Photo Supply Co., Rochester, N. Y., (1937).

416 O. O. CECCARINI

5 "Color Separation Negatives," Brit. J. Phot. Almanac (1937).
4 "Trichrome Printing by the Autotype Carbro Process" (obtainable in
U. S. A. through George Murphy, Inc., New York, N. Y.).

7 "Color Printing with Eastman Wash-Off Relief Film," Eastman Kodak Co.,
Rochester, N. Y.

8 "The Chromatone Process," Defender Photo Supply Co., Rochester, N. Y.

9 NAMIAS, R.: "La Fotografia a Colori," // Progresso Fotografico (Fifth Ed..
1930), Milan, Italy.

10 VON ARX, R.: "The Mordant Dye Printing Process" (Proceedings of the
Seventh International Congress of Photography, London, 1928), Heffer & Sons
(1929), Cambridge.

11 WALL, E. J.: "Practical Color Photography," Amer. Phot. Pub. Co., Boston,
Mass.

14 NAMIAS, R.: "La Collografia," // Progresso Fotografico (1925), Milan,
Italy.

PFUND, F.: "Handbuch der Modernen Reproduktions Technik," Verlag
Von Klimsch & Co., II (1927), Frankfurt A.M.

WILSON, T. A.: "The Practice of Collotype," Amer. Phot. Pub. Co. (1935)
Boston, Mass.

lf MAYER, E.: "Bromoil Printing and Transfer (in German)," Amer. Phot.
Pub. Co. (1923), Boston, Mass.

ADDITIONAL BIBLIOGRAPHY

14 WALL, E. J. : "History of Color Photography," Amer. Phot. Pub. Co. (1925),
Boston, Mass.

15 WHEELER, O. : "Color Photography," I. Pitman & Son (1935), London.

18 NEWENS, F. R.: "The Technic of Three-Color Photography," Blackie &
Sons, Ltd. (1936), London.

"HUBL, A.: "Three-Color Photography," A. W. Penrose & Co. (1904),
London.

18 DUNN, C. E.: "Natural Color Processes," Amer. Phot. Pub. Co. (1936),
Boston, Mass.

19 KLEIN, A.: "Color Cinematography," Amer. Phot. Pub. Co. (1936), Boston,

Mass.

DISCUSSION

MR. SOLOW: I am sure that Mr. Ceccarini would be interested in knowing
that the Collotype process is used extensively hi this country for the production
of three-color lobby displays. The process has been adapted to high-speed
rotary presses by the use of bichromated gelatin coated on thin sheets of alumi-
num, and prints as large as 40 by 60 inches are possible.

MR. CECCARINI: By Collotype in this particular case I mean the "typical
small installation" employing printing plates of bichromated gelatin without the
use of any photomechanical process screen. The reticulation of the gelatin coat-
ing is produced by treatment with a mixture of water and glycerin.

MATHEMATICAL RELATIONS BETWEEN GRAIN, BACK-
GROUND NOISE AND CHARACTERISTIC CURVE OF
SOUND-FILM EMULSIONS*

W. J. ALBERSHEIM**

Summary. — Computations and measurements show that the background noise of
film can be interpreted as the superposition of two types of noise: surface noise, and
grain noise. The surface noise power decreases with the square of specular trans-
mission; the grain noise power reaches a maximum at 50 per cent transmission.
Accordingly, it is found that under conditions of variable-width recording surface
noise is predominant; for variable-density recording, grain noise is the main factor.
The average area of the grains or grain clusters can be calculated from the signal-to-
noise ratio; their average volume from the total weight of silver per square centimeter
at a given density; their average thickness from the quotient of volume and area.
For equal grain sizes, surface exposure such as obtained by ultraviolet illumina-
tion is definitely noisier than penetrating exposure.

Upon the basis of random three-dimensional distribution of sensitized grains and
of the quantum theoretical findings of previous investigators, the shapes of H&D
curves were calculated. The assumption that a halide grain is sensitized by a single
photon leads to a toe shape that is more rounded than is found in practice. The
actual shape of the characteristic from toe to shoulder is accounted for by the assump-
tion that it takes two photons to sensitize a silver halide grain. It is expressed by the
equation:

n £>» r ce i - e~* , i

D = y- €-<"• - e~« - I - dx \

In <p [_ Jer x

in which r represents the translucence of the unexposed emulsion to the actinic light.
The experimental fact that the straight portions of H&D curves obtained from the
same emulsion at various gammas originate from a single point which is depressed by
bromide content is explainable by taking into account the fact that the emulsion con-
tains silver halide grains of more than one size and speed.

Important inventions and new technical processes are usually intro-
duced as new "arts" in the language of the patent law, as well as in
fact. The word implies that the details of the process are not gen-
erally known and require a special skill or instinct for their operation.
As practical knowledge is gained, the new process becomes a "craft."

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
May 20, 1937.

** Electrical Research Products, Inc., New York, N. Y.

417

418 W. J. ALBERSHEIM [J. S. M. P. E.

This is the stage at which the trained foreman, with his long years
of shop experience, is indispensable. A large number of quantitative
rules and secret processes is being worked out; but they are mostly
rules of thumb derived from practical results without understanding
of the inner causes. Finally the process becomes a "science," the
many quantitative relations are analyzed and are found to be con-
sequences or special cases of a few basic principles; thus, technical
results and possible improvements become predictable and subject
to engineering.

In the motion picture film industry, the same development is taking
place. The early publications in the pioneering age dealt largely
in observational qualitative terms. Large-scale properties of the
emulsion were given vague names such as "speed" and "contrast,"
and the small-scale properties of film grains were described as "boil-
ing" and "graininess." The density characteristic was roughly
divided into the "toe," "straight line," and "shoulder" regions.

The advent of sound-film recording, with its high and technically
well defined requirements, brought about more or less rigid quanti-
tative definitions of film characteristics. The sound engineer thinks
of the properties of the film emulsions in functional terms. The
curvature of the density characteristic determines amplitude dis-
tortion, harmonic overtones, cross-modulation, etc. The micro-
scopic qualities of the emulsion and of the film base become audible
as high-frequency losses and as background noise. All these effects
have been quantitatively measured by the various companies active
in the industry and have resulted in a number of jealously guarded
secret processes on the side of the film manufacturers, and, on the
side of the film users, in various methods of sound-film recording and
reproducing attempting to utilize the given film characteristics in
the most efficient manner.

If we now attempt to correlate this abundant practical informa-
tion, we find that the directly measured and technically important
qualities, such as density, noise-level and noise frequency spectrum,
are large-scale properties; and yet we know, by microscopic inspec-
tion, that they are caused by the additive action of millions of small
silver grains. We are dealing with a problem similar to that solved
by Clerk Maxwell, who interpreted all the large-scale properties of
gases, such as pressure, heat expansion, entropy, and viscosity, as the
combined effect of countless molecules in random motion.

We need not concern ourselves with the exact shape and size of

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 419

the individual film grain but with the resultant effects of their sum.
In other words, all the observed properties of film must be explain-
able, and perhaps new relations may be found, by applying statis-
tical calculation to the emulsion of silver grains. The present paper
aims to give some of these statistics.

(1) VOLUME RANGE AND GRAIN SIZE

Our first problem is to decide what degree of statistical freedom
to apply: do the silver grains form a 2-dimensional array like the
small stones in a mosaic picture, or a 3-dimensional array like the
berries in a flat dish of huckleberry pie? Both these types of ar-
rangement may be approximated in reality, depending upon the
intensity and penetrating power of light and development. Let
us derive the laws for both types of image and compare them with
experimental facts.

We begin with the following simplifying idealizations, part of
which we may drop as we go along: (7) The image is composed of
silver grains uniform in size and shape, completely opaque, and
large compared to the wavelength of light; (2) the light falling into
the photoelectric cell is completely specular, so that we may neglect
all diffraction effects.

Case 1. Two-Dimensional Array (Surface Image}. — The assump-
tion of a 2-dimensional array is expressed in the relation:*

N-M _ M Ma

N N A

Regarding the slit area as a mosaic of M' black "grains" and N — M'
white "gaps" we find that the probability of finding a given mosaic
figure consisting of M' grains equals

(M\M'/N — M\N~M>
f ) (^-^) = (1 - V' T*-*" (2)

The number of possible permutations without change of M' equals

N!

^(M > M' l(N - M') !

and therefore the total probability of finding M' grains

M*"(N - M)"-*' JV!
"' : M' l(N - M') \NN

(4)

* See list of symbols, p. 444.

420 W. J. ALBERSHEIM [J. S. M. P. E.

The probability of finding M' + 1 grains equals

M*'+i(N - M)x-x'-lNl
M'+l (M' + 1) ! (N - M' - 1)1 NX

Hence

Pfr'+i) _ M(N - M') = N- M' . M_ . M'

_

P(M) (N - M)(M' + 1) N - M M' M' + 1

=ln(l - _^_-^ - In ( 1 + ^)

- In ( 1 + i) (7)

Since the number of grains is very great and the variations in number
relatively small one may approximate:

d In P(M)' d In P(MY 8M _ SM[ N 8M

AM' d8M N - M M = (N - Af)M

by integration one finds

(10)

in which Pa has the value of equation 4. From equation 1 one
finds that

5M = -N(8T) (11)

Hence

This is a typical probability function, from which one finds

0.477 2T - 0.675 - ~ = 0.675T -£.

. Three-Dimensional Array (Depth Penetration of Image).
By a reasoning identical with that of case 1 we find again

M = 0.675^^ =0.675^(1- |)M

From this probable deviation.of grain number one finds the density
or transmission deviations by the following reasoning: Imagine

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 421

that the emulsion, which may have a thickness of y cm., is divided
into a great number of extremely thin slices dy. Each slice is thick
enough to accommodate only one grain layer. The slicing knife is
supposed to be slightly blunted so that no grain is cut but is pushed
into the next lower or higher slice. Since the grains are distributed
at random, one may regard each slice as a diffuse absorption screen.
The density of the entire emulsion is then the sum of all the single-
slice densities:

D = -s Di (is)

or, in the limit

D = fydD/dy.dy (16)

Jo

Each layer is subject to two-dimensional reasoning, and, ac-
cordingly :

1 - dT = ^dM (17)

d De = -In dT - 1 - dT = -. dM (18)

A

De= f dD. = \M = Q (19)

IAD,! =

= -. AM

AF = TabM = 0.675 ** f - m >a*M

_ M ja3M
~~N ' A/"^"

A*

I TUT 1 n „

= 0.675

The fraction M/N now means the spatial silver content of the
emulsion in cm* Ag per cm3 emulsion, which is a very small fraction.
Hence one can approximate

Ar = 0.675 T-J^ . V2i3~D = 1.022 T-Jj ^/D~ (23)

In comparing equations 13 and 23 one may first consider the proper-
ties that they have in common :

(1) The probable deviation of the transmission is inverse to the
square-root of the scanning area. This means that the ratio of
noise-power to the power of a fully modulated low-frequency signal
decreases inversely to the slit area.

422 W. J. ALBERSHEIM [J. S. M. P. E.

(1.1} Doubling the track width must increase the volume range

3 db.

(1.2) Doubling the slit spacing must likewise decrease the relative
noise-power 3 db.; but for a given film-scanning speed it
also cuts the frequency range in half. Hence it is deduced
that the noise-power must be evenly spread over the entire
frequency band; provided that each cycle of the highest
scanned frequency contains a large number of grains.

Both these deductions have been verified by engineers of
the Bell System for frequencies over a few hundred cps.;
that is, for wavelengths smaller than l/i6 inch or so.

Low frequencies are subject to disturbances that are not
random in three dimensions and partly not random at all.
Such disturbances are, for instance, the minute "ripples"
hi the flow of emulsion during the coating process and the
ever-present sprocket-hole modulation of 96 cps.
(2) The probable deviation (or noise amplitude) increases with
the square root of the grain area.

(5) The probable deviation due to silver grains vanishes for com-
pletely transparent film as well as for completely opaque film.

This result is logical, but it is known from experiment that even un-
exposed and undeveloped film from which all silver has been dis-
solved by the fixing process produces a considerable amount of noise
due to inhomogenities of surfaces, emulsion, and film base. Fre-
quently these noises are lumped under the name of "surface noise."

One must regard this surface-effect as an entirely separate source
of noise which contributes its own density as well as density deviation.
Since the deviations are of a random nature they have to be combined
by root-mean-square addition. One may write:

A*Z> = A*£>. + AW0 = K + &*D9 (24)

Consider next the differences between the two cases, in order to
decide which corresponds more closely to actual conditions.

(4) Relation of silver weight to density. For Case 1 one finds
from equation 1:

M, - tf(i - r) (25)

and in view of

A. ---? (26)

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 423

Atl = ^ • (1 - T) ' (27)

This implies that for high densities the silver content approaches
the fixed maximum value Vd/a.
For Case 2 one finds from equation 19

M* = D.N (28)

and

_ VPD. _ VPD
A<* ~ IT ~ 23~a

Equation 29 indicates that the silver weight is directly propor-
tional to density. Investigations conducted at the Eastman Kodak
Laboratories1 confirm this relation for normal types of emulsion
and exposure. This is weighty evidence in favor of the three-
dimensional statistics. And yet there are some recording methods
in which an effort is made to enforce surface images for the sake of
better high-frequency definition. Several years ago such tests
were made with the use of dyes in the emulsion that strongly absorb
the photographically active rays.

Another recording method illuminates the film with light of short
wavelength, which is highly attenuated by the standard motion
picture film emulsions. In order to find out how closely the second
method approaches the ideal two-dimensional case, the ERPI
Engineering Department recorded variable-density frequency test-
films, first in the normal manner, then through filters that limited
the light to the violet end of the spectrum, and compared frequency
characteristics and volume ranges.

No difference in frequency characteristic was found; however,
this result is not conclusive, since the optical system was corrected
for normal incandescent light and was refocused but not modified
for the filtered light.

The result did show, however, a 4-db. increase of background noise
in the "violet" recording which we shall compare with the theoretical
volume range.

Volume range is defined as the difference in db. between the ground-
noise power and the power of a sine wave at overload level. For
densities smaller than 0.3 the volume range equals :

V, = 20 log n e£) (**)

424 W. J. ALBERSMEIM

For densities larger than 0.3 it is

[J. S. M. P. E.

(30b)

Applying this relation to 13 and neglecting the surface-noise, one finds
for the two-dimensional case

~ (31a)

3.4

+ 10 log y + 10 log

VKb = 3.4 + 10 log - - 10 log ( 1

(31V)

FIG. 1. Computed relative volume ranges.

Applying 30 to equation 23, and again neglecting the surface-noise,
one finds

- 10 log D (32a)
(32b)

VRu = -0.2 + 10 log +20 log

VRb -- 0.2 + 10 log (\ - 10 log D

Omitting the constant term 10 log (A /a) these volume ranges have
been plotted in Fig. 1. It is seen that regardless of the type of ex-
posure the maximum volume range is obtained at the density 0.3. Un-
fortunately, this optimum is difficult to realize due to the curvature
of the toe characteristic.

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS

425

1

I

« o

426 W. J. ALBERSHEIM [J. S. M. p. E.

At specular densities near 0.7 which are normal for variable-
density negatives, the calculated volume range of the surface exposure
is about 4 db. lower than that of the depth exposure, a result that more
than offsets any possible improvement in high-frequency response.

This agreement of theory and experiment strengthens the belief
that surface exposure may be approached by deliberate measures,
but that the normal type of sound-film exposure can be classed as
depth exposure within the meaning of our theory.

Our experiments with regard to the relative noise-level of surface
and depth exposures were conducted with the variable-density method.
The variable-width method works with markedly different condi-
tions. In the ideal case, one-half of the negative track is entirely
unexposed aird therefore grainless, the other half highly overexposed
and therefore practically opaque. In the unexposed half of the track
the actual noise is "surface noise," which is unaffected by the nature
of the exposure. In the dark portion, equation 13 indicates that while
the noise power is higher for surface exposure than for depth exposure,
it approaches zero for zero transmission.

The trouble is only that with a single layer of grains it is difficult
to approach zero transmission. Our "two-dimensional statistics"
were based upon the assumption that the mosaic of film grains
can completely cover the emulsion. This would be possible if all
the grains were rectangles, or triangles of uniform size and shape.
Actually they are crystals of irregular size and shape which might be
visualized as a mixture of microscopic poker chips, domino bars,
triangles, etc. Obviously one can not cover an area by a single
layer of such grains without leaving irregular gaps which are decided
deviations from the desired blackness.

The more one approaches ideal surface exposure the more noise
will be transmitted by the dark portion of the negative track. In
the print these gaps will be shown as black dots on the light side of
the positive, and if the print, too, is a surface image, its dark side
will have new gaps which further increase the noise.

As a final check of the three-dimensional theory, we derive the
characteristic of noise-level versus specular density, taking into
account the surface noise. We have

De= -A(lnr) = ~~ (33)

Hence equation 24 can be transformed into

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS

(AT)2 = r2. A2/),. + A*r,,
In view of equation 23 one finds

(AD2 = r2 [" A2!).. + 1.05^- D~\

Expressing the noise power level in db., one finds:

LD = 10 log(AD2 = L. - 20DX + 10 log Dt
In this equation

La = 0.2 + 10 log (^\

427

100 - A2D,

a

Z>. - Z> + 6 - A2/),
a

In Fig. 2 is seen the curve

L 20D + 10 log

(35)
(36)

(36a)
(36b)

(37)

Comparing equations 36 and 37 it is seen that L0 corresponds to
a shift parallel to the ordinate axis fixing the absolute noise-level,

FIG. 4. Film noise tests.

and the substitution of Dx for D corresponds to a shift along the
abscissa, determined by the ratio of ground-noise to maximum
grain-noise.

Since 36 is the most general case, it is claimed by the theory that
any experimental curve of ground-noise level versus specular density

W. J. ALBERSHEIM [J. S. M. P. E.

can be made to coincide with the curve of Fig. 2 by a parallel shift
without tilting. Figs. 3 and 4 show superposition of function 37
on tests made with Eastman emulsions 1301 and 1359, respectively.
The agreement is very good and well within the limits of observa-
tional errors. The only region where systematic differences of about
1 db. seem to occur is at extremely low densities, in the "toe" region
of the H&D curve. This is partly due to the fact that this region
approaches surface exposure, partly to the fact that the grains are
not all of one size. At low exposures the largest grains have the
greatest probability of being hit by photons and thus increase the
average grain size, as discussed below in the section on Bromide
Depression.

In view of the fact that the low-frequency noises are not random
effects, the noise of the test-films shown in Figs. 3 and 4 was measured
with a transmission circuit including a one-section, 500-cycle low-
pass filter.

By measuring the level difference between noise and a known
amount of low-frequency modulation, one finds the absolute volume
range and, therefrom, the grain area.

The absolute levels are indicated on Figs. 3 and 4; they are subject
to an error of 2 db. Based upon these figures the grain area of the
high-gamma film, test No. 153, is computed in the following manner:

From the amount of lateral shift necessary to superimpose Fig. 2
upon the experimental curve:

Dz = D + 0.02 (38)

From 36 one finds

L0 = LD + 2QD, - 10 log Dt (39)

L0 = -55 + 20(0.735 + 0.03) - 10 log(0.735 + 0.03) = -38.5 (40)

log j = 0.1 (L0 - 0.2 - 20X0.03) = -3.93 (41)

Since the slit area was

A = 80 square-mils, (42)

a = 1.0 X lO-8 sq. inches = 6.4 X 10~« cm.1 (43)

Assuming a round shape of the grain, one finds for the mean grain
diameter

d = Vl-27o = 1.1 X 10-4in. = 2.9 X 10-4cm. = 2.9/u (44)

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 429

For the low-gamma film, test No. 154, one finds in the same manner

a = 3.04 X 10-o in.2 = 2.0 X 10 ~» cm.1 (45)

d = 6.2 X 10~s in. = 1.6 cm.~« = 1.6/t (46)

The values 44 and 46 are of the right order of magnitude according
to published figures and our own microscopic inspection.

Having thus found the cross-sectional area and diameter of the
grains, it is possible to find the average thickness (or depth) of the
grain by weighing the amount of silver per unit surface. By defi-
nition we have

Aa = QyaP (47)

In film No. 153 we found

A,rf = 0.97 . D, = 1.21

Ae = 1.3 X 10~4 g cm
p = 10.5 g cm~3

Hence :

= 2.3 X 1.3 X 10 ~*
y' " 1.21 X 10.5

2.4 X 10^s cm = 0.24/u (4Sb)

The average thickness is about 10 tunes smaller than the average
diameter. This indicates a flaky character of the film grains, caused
conceivably by the stresses in flowing the emulsion on the base in a
thin layer.

(2) LATENT IMAGE, H&D CURVE

Since the statistical viewpoint accounts well for the observation
connected with film noise and grain size, we now apply it to
the useful purpose of the film, that is to the formation of the
latent photographic image and its development. The three-dimen-
sional method of attack is applied again. It consists in subdividing
the emulsion into a great number of thin layers, each of which con-
tains sufficient grains to be subject to two-dimensional statistics and
each of which acts as a diffusing screen on all others.

We must now make some assumptions with regard to the photo-
chemical mechanism by which a silver halide grain is modified to
form the latent image. Our starting point is the application of
quantum mechanics to photographic theory as set forth by J. H.

430 W. J. ALBERSHEIM [J. S. M. P. E.

Webb of the Eastman Kodak Research Laboratories in a recent paper.2
The general concept is about as follows: A halide grain, after
cooking in the organic gelatin, has on its surface one or more "con-
centration specks," which act as sensitizers. No matter where the
grain is hit by a photon of light, there exists a certain probability
that an electron may be knocked into an energy level at which it can
freely travel through the grain as if the grain were metallic. It
finds its way to the concentration speck, attaches itself to it, and
thus becomes in some manner that is not yet fully explained, the
starting point or "nucleus" for the action of the developer. Inci-
dentally, there exists a (much smaller) probability that an electron
already attached to the concentration speck is knocked loose again
by a further photon impact. This photographic reversal effect is
not taken into account in this paper because it is negligible at the
exposures used for sound-film recording. Consider now a slice of
emulsion of unit area and of the thickness dy. It contains h dy/ Y
halide grains of a photographic "speed" or sensitivity 5. Let it be
exposed to an illumination Ey. How many grains will be activated
by photons?

According to the laws of mass action

from which one finds

drv = ~ (1 - t-'B»)dy (50)

The illumination is a function of depth. Assuming that the
turbidity and light absorption are uniform throughout the emulsion,
one finds

and

£„ = £„€-«» (52)

Hence

drv = p(l - e-«V«-«»)dy (55)

and finally

Oct.. 1937] MATHEMATICAL RELATIONS IN EMULSIONS 431

This integral can be simplified by introducing the translucence

factor

x = e-«» (55)

and the "relative exposure"

e = sEy (56)

one finds

(1 - t~")dx

- — H <57>

This equation indicates the total number of activated grains per
unit area. If one assumes that after development each activated
grain is transformed into a silver grain of area a, one finds for the
density, in view of equation 19,

D, = -0.434,— P * ~ * "• dx (58)

This, then, is the density-exposure function.

When plotted upon a logarithmic exposure scale, it yields the
H&D curve according to the "single hit" theory. The integral
58 has no general solution, but it can be evaluated by series develop-
ment. Correct and convergent for all exposures is the series

r« i - «-

JO X

dx = f(e) ** e H h (59)

2.2! 3.3!

which has been plotted as Fig. 5 and which solves the integral 58 in
the following form:

Series 59 becomes cumbersome for values of e greater than 4.
Fortunately at these higher values the series can be approximated
by the value

e - -T^l +3^7 - + = In e + 0.592 (61)

If (er) as well as e exceeds 4, Z>i approaches the end value

, -0.434 ha M , / M

i-'ico == : lln e — \n\eT) \

In T

432
Hence

W. J. ALBERSHEIM

For very small exposures,

[J. S. M. P. E.

(63)

(64)

.2 3 * .f .(. 1

j \ II

FIG. 5. Numerical values of integral
f unction /(e).

or

The gradient of the H&D curve is

dD . ht

[e-T« —

dloge1 -Inr ' . -logr1'

This gradient reaches its maximum value T, when

In

1 -

r = -

lOgT

-— r

logr L

(66)
(67)

(69)
(70)

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS

Equation 69 gives a functional relation between F, D and T so that
each can be calculated from the two others. For instance, if one
knows F and D from an experimental H&D curve, one can find T
from the function <p:(r), which has been evaluated in Fig. 6. Know-
ing T and D one can plot the H&D curve from equation 63 and its
series developments.

This is shown for values of D and F that are normal in sound-film
development in curve A of Fig. 7. It is seen that the general shape
resembles an H&D curve but that the toe is too round.

The difference between experimental and computed curves be-
comes more apparent when density or transmission is plotted against

FIG. 6. Translucency constant as a function of E maxi-
mum density (single-hit).

a linear exposure scale, as one usually does for the inspection of
"toe records." This is shown in curve A of Fig. 8. The curve
indicates for low exposures a linear decrease of transmission with
exposure in accordance with equation 65. This toe shape disagrees
with observation to such a degree that the "single hit" theory in
the above form is unsatisfactory.

Another fact that contradicts the relations deduced from the
"single-hit" theory is the practice of astronomers and spectographers
which consists in "prefogging" their plates for maximum sensitivity
to faint illumination. From a differentiation of 63 with regard to
e, one would find for the density-exposure gradient:

dD_
de

lOgT

(71)

434

W. J. ALBERSHEIM

[J. S. M. P. E.

which has its maximum at zero exposures (unfogged plate!).

The weight of evidence indicates that for very low illumination
the density increases with the square of exposure.

If one attempts to reconcile this experimental fact with the quan-
tum mechanical viewpoint set forth by the above-quoted paper,2
one is led to the conclusion that a grain must be hit by at least two
photons in order to become developable.

It is not within the province of this analytical paper to find the
photochemical mechanism that requires two mobile electrons for
activation. One possible explanation might lie in the fact that in

FIG. 7. Computed H&D curves.

many compounds the halogenes act as if they had not only one
chemical valence but were multivalent with a preference for the odd
numbers. One might imagine some formula such as

3AgCl + 2e~ = AgjCl + 2C1~

but we must leave this for investigators in the field of physical
chemistry to decide.

The "double-hit" hypothesis leads to formulas for density, F,
etc., in a manner quite analogous to the single-hit calculations. In-
stead of equation 49 above, one has two unknowns, dr and dg, and
two equations:

d(dr) = s (^ - dr\ dE (49)

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS

d(dg) = s(dr - dg)dE
One finds

dg = [1 - (1 + iE,)t-"*]j.dy
In view of 52, 55, and 56:

,dx

Yu

= r +

lnrJT

435

(72)

(73)

(74)
(75)
(76)

CURVE A - 5IN6LE-HIT THEORY
CUKvt B - SooHt-MiT TMIORY

— — — S£ (CURVE A)| R6L),TIVE EXposuRtx
— r— 45e(CuRvEB)j k

•/ .2 .3 .4

FIG. 8. Computed toe characteristics.

A

g r + hLT (t T « e)

(77)

Assuming again that the development transforms an activated silver
halide crystal into a silver grain of the cross-sectional area a one finds

or

or

^lnrve

(75)

= ^Tr \_<~' ~ *~'T + f (1 ~ 6~l)d(ln -V

436

W. J. ALBERSHEIM

[J. S. M. P. E.

In evaluating this equation one may use either the previously
given formulas for A and find separately the values for e~e + e~e;
or for small values of e, the combined series development.

(82)

FIG. 9. Translucency constant as a function of gamma
and maximum density (double-hit).

which has the required square-law properties. The gradient of the
H&D curve equals

D,

log r

[(1

(55)

The maximum value of e is reached for

-2hiT

One finds by combining equations 83 and 84,

IT 2

£>«, T/, 2r \ r=T / 21nr\ TZ^~|

12=—: — ( 1 ~ - In T IT - ( 1 - )r

log T L\ 1-7- / \ 1 - r)

Oct.. 1937] MATHEMATICAL RELATION'S m EMULSIONS 437

and

Again T, Dm and r are inter-related and from T and Dm one can
ind T from function <pi(j) which has been plotted as Fig. 9.
Knowing D and r one can plot the H&D curve from equation 79.
Curve B of Fig. 7 shows the curve thus obtained for the same
rallies of £>_ and T as curve A.

Curve B on Fig. 8 shows the toe characteristic of the same H&D
•urve. It has been compressed laterally by a factor of 4: 1 in order
o reduce it to a convenient scale.

It is apparent that curves B look like familiar H&D curves. As
a matter of fact it has been possible to match closely all experimental
sensitometric curves for high and low gammas that are reasonably
free from fog. The accuracy of the match is commensurate with
the accuracy of observation, and improves for experimental curves
that are the averages of many well agitated sensitometer strips.
The densities and gammas should be specular values.

Fig. 10 shows as solid tines typical curves for high and low gamma
developed in positive bath, measured several years ago; the visual
diffuse values were accepted because the ratio of specular to diffuse
gamma was not known for this particular case; it usually approxi-
mates a constant value of about 1.35. The small circles show the
calculated values; the closeness of agreement is evident.

In analyzing equation 79 one sees that outside of Dm, which de-
termines the total height of the H&D curve, the only free parameter
is the transhicence T. The smaller T, the longer the straight-tine
portion of the H&D curve, as can be seen by inspection of equation
S3. From this it may be concluded that a certain increase of tight
absorption in recording and printing is beneficial — as long as it does
not approach the conditions of surface development, which reduces
Dm instead of increasing T. It would seem best to increase the ab-
sorption by adding to the thirlcnpss of the emulsion. High density
and contrast with low ground-noise should be obtained by a great
number of small grains rather than by a few large grains. This,
of course, will somewhat reduce the speed of the emulsion and, if
thick emulsions are used, the picture detail.

438

W. J. ALBERSJJEIM

[J. S. M. P. E.

fit]

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 439

(3) DEVELOPMENT CHARACTERISTIC AND BROMIDE DEPRESSION

The next test of the statistical method is its application to the
theory of development and to the relations between characteristics
produced from identical latent images by development for different
lengths of time or in different developing agents.

Equation 83 indicates that in the region in which e is much larger
than one but er much smaller than one, the number of activated
grains in the latent image increases in proportion to the logarithm
of exposure. This, then, is the "straight-line portion of the H&D
curve." It can be expressed by the approximate formula

g = k(log e — log i) (87)

Our simplifying assumption of uniform halide grain size and compo-
sition has the natural consequence that, regardless of nature and
duration of the development, the developed grains are also closely
grouped around a uniform value a, and hence

Da = ka(log e - log *') = T(0) (loge - log») (88)

If one permits a to change by varying the length of development,
Da when plotted as a function of the logarithm of exposure, describes
a family of straight lines originating in a common point on the
exposure axis

D = o, e = i (89)

This family of lines is shown as Fig. 11 (a). For bromide-free de-
veloper this is a good description of the actual experimental result.

If, however, the developer contains free bromide, the various
straight lines seem to originate from a common point below the
exposure axis and "depressed" by a density D0 as shown in Fig.
11(6). This relation is amply discussed in the Eastman Kodak
Monograph No. 23 on the theory of photography, to which we shall
refer for additional experimental facts.

In order to explain this behavior one must give up the idealization
that all halide grains are of uniform size and nature, and must take
into account the fact that the actual halide grain areas are distributed
around an average value in a probability function which, again, is
subject to statistical analysis. Since photographic speed contains
the probability of the photon's scoring two direct hits on the grain,
it varies approximately with the square of the halide grain area.
The contribution of the grain to the density varies with the area of
the developed grain. Strictly spaeking, one ought to compute the

440 W. J. ALBERSHEIM [J. S. M. p. E.

H&D curve differential for each particular grain size and integrate
over all grain sizes. Fortunately, this integration does not greatly
affect the shape of the actual H&D characteristic because even
with the simplified assumption of uniform grain size, equation 79
is an integral of the density differentials in a great number of thin
emulsion slices exposed to exponentially decreasing light intensities.
The density differentials "mix easily."
The analytical description of Fig. 1 1 (6) is

D = r(log e - log 0 - D0 (90)

In order to keep log i and D0 constant regardless of development
time, there must be a definite relation between the areas of silver
grains being developed from halide grains of different sizes. This,
then, forces us to investigate the equations for the velocity of de-
velopment. The first step consists in finding the functional relation
required by Fig. 11(6) and equation 90.

Instead of considering the innumerable different halide grain
sizes, let us limit the number of grain sizes to 2, because this will
suffice for an analysis of the problem. Assume, therefore, that D
is built up of two components of the type 88. Their sum must
conform to equation 90; hence:

D = £iai(log e — log ii) + £2a2(log « — log iz) = T(log e — log i) — ,D0 (91)
Since this is true regardless of the value of e,

r = kiai + k&z (92)

and

&2 log t — log i-i log i — log t'2

Since 02 can never be negative, equation 90 can be satisfied only for

ai > log * - log i
and for

Dn

log i, - log i

For high values of T the constant subtraction term of 93 becomes
relatively unimportant, and az outgrows ai. Forgetting mathe-
matics for the moment, let us form a mental image of the mechanism
involved. Assume that each halide grain has one sensitizing con-
centration speck on its surface. The larger grains have a greater

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS

441

chance to be hit by light, hence a smaller "inertia." For any given
exposure, a fixed proportion of large and small grains is activated.
As development of each grain begins it must proceed inward from
the small concentration speck, and in the early stages of development
all the silver grains grow at the same rate. Thus the low-r, H&D
curve acts as if the weight of the large and small components were
equal, and the inertia point is halfway between those of large and
small grains. As development proceeds, the smaller halide grains
become fully converted into metallic silver, and the larger halide
grains begin to outstrip them in silver deposition. Thus the H&D
curve, following the weighted average, shifts nearer and nearer the
lower inertia point of the larger halide grains.

There remains the question as to the chemical process that pro-

5 to if 20

FIG. 12. Development characteristic.

duces grain-size ratios in accordance with equation 93. The answer
may be deduced from inspecting development-velocity curves typical
of bromide developers. In Fig. 12 the circles show observed values
copied from Fig. 27(^4) of the Eastman Kodak monograph.3

The predominant shape approximates an exponential approach to a
saturation value, like the voltage at the terminals of a condenser
that is being charged by a constant voltage through a resistance.
But there is a time delay, which A. H. Nietz calls induction period,
and a tendency towards a square-law incr8ase (as if a small inductance
were added to the resistance in our electrical analogy) which strongly
suggest a 2-phase chemical process.

As a working hypothesis assume that the relatively fast first phase
consists in dissolving and breaking down the halide crystals so that
silver ions are present in solution in the little hole or crack previously
occupied by the halide grain. It is this first phase that begins at a

442 W. J. ALBERSHEIM [J. S. M. p. E.

rate independent of grain size. This dissolving process is slowed
down by the presence of free bromide in the solvent.

As soon as silver ions are in solution they are precipitated at a rate
characteristic of the developer and deposited upon the walls of the
grain hole and of adjoining cracks in the emulsion. Since this is
akin to a "plating" process, it offers an explanation for the thin and
flake-like structure of the silver grains (eq. 48V) which was previously
deduced from the "photometric constant"; that is, the weight of
silver per sq. cm. divided by the density.

Putting all the above reasoning into the mathematical language
of a mass-action differential equation, one finds :

dt hb
%-C(j-o) (97)

in which b expresses the retarding effect of the bromide and c the rate
of silver deposition, or generally the speed of the second phase. The
solutions are:

(98a)

the initial rate of change of which displays the required independence
from h, and

•-»[' + r=^B --""• - r=TB '""] <"»>

If the dissolving or ionizing phase proceeds with much higher
speed than the depositing phase, the second term of 98b will soon be
negligibly small, so that 98b can be approximated by

This can be interpreted in the form:

a =

in which the "induction period" is

A* -- iln(l-CM)-*6 (101)

In the example of Fig. 12, this period amounts to 1.4 minutes.
The other way of writing equation 99 is

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 443

If two sizes of halide grains were present in the emulsion,

__*!__ M _ t-0t] - Ckl*

and

*? n - *-ct] -

from which

*,(! - Chib) Clhbfo - hi) „ „ ,inc.

a-i = di j-j- .• -=-=- — — AI Ci — A.2 (.105)

This equation is independent of time ; it has exactly the form of
equation 93, which corresponds to the common origin of all straight-
line portions from one "depression point."

By comparing 93 and 105 one finds

1 -

(log i — log iz) depends upon properties of the undeveloped halide
grains. If one maintains, for instance, the previously introduced
assumption that the speed is proportional to the square of the halide
grain area, then

**<-**- ^ van

in which ki and kz denote the relative abundance of grain areas hi
and hz. One thus finds that for a given emulsion all terms but the
first on the right side of equation 106 are constants. Therefore

X1T

Do = Constant • ^-^ (108)

1 ^~

or, for small depressions,

D0 = Constant • Cb (109)

Comparing this with equation 101,

DO = Constant • M (110)

For a given emulsion, the bromide depression is approximately
proportional to the induction time and, of course, to the free bromide
content.

If one considers various emulsions, one finds from equations 106
and 107 that the bromide depression is proportional to (hi — h^)

444 W. J. ALBERSHEIM [J. S. M. P. E.

and to log (h^/hi). Both these factors approach zero for the limit of
uniform grain size; for small values, the depression is therefore
proportional to the square of the mean relative variation of the
silver halide grain size.

The statistical method applied to the microscopic silver halide
grains before, during, and after development has thus accounted for
the large-scale phenomena of noise, contrast, speed, and develop-
ment characteristics. It has predicted some previously unknown
relations, which were verified by experiments, and others that still
remain to be tested.

LIST OF SYMBOLS
Symbol Dimension

A Area of scanning slit cm*

a Area of silver grain cm2

d Diameter of silver grain cm

N Maximum silver grain number in slit

M Average silver grain number in slit

M' Instantaneous silver grain number in slit

T Average transmission

T' Instantaneous transmission

Dt Average density, base e ( — In T)

D Average density, base 10 ( —log T)

D' Instantaneous density, base 10 (—log T)

SM Actual deviation of M

ST Actual deviation of T

SD Actual deviation of D

AM Probable deviation of M

AT Probable deviation of T

&D Probable deviation of D

P Probability

V Volume of emulsion under slit cm1

v Volume of a silver grain cm1

W Average weight of silver under slit g

w Weight of a silver grain g

p Density of silver g cm~3

Ag Weight of silver per cm2 of sound track gcm~2

Y Thickness of emulsion cm

y. Thickness of grain cm

L Power level db

n Maximum silver grain number per unit area cm"2

m Average silver grain number per unit area cm ~2

Q Average silver grain surface per unit area

T Translucence of unexposed emulsion

Oct., 1937] MATHEMATICAL RELATIONS IN EMULSIONS 445

h Area of unexposed halide grain cm*

y Extension in depth cm

r Halide grains hit by at least one photon

g Halide grains hit by at least 2 photons

5 "speed" factor or "sensitivity" dyne"1

u Turbidity cm"1

E Exposure dynes

e Relative exposure

b Bromide content

c Rate of silver deposition sec"1

7 Area of dissolved silver ions in grains cm2

« Basis of natural logarithms

In Natural logarithm, basis e

log Common logarithm, basis 10

* Inertia

REFERENCES

1 Ross, F. E.: "The Physics of the Developed Photographic Image," D. Van
Notirand Co. (New York), 1924, p. 46.

2 J. Opt. Soc. Amer. (Oct., 1936), p. 367.

3 NIETZ, A. H.: "The Theory of Development," D. Van Nostrand Co. (New
York), 1922, pp. 35, 77.

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus are held, in which various manufacturers of equipment describe and demonstrate
their new products and developments. Some of this equipment is described in the
following pages; the remainder will be published in subsequent issues of the Journal.

LABORATORY EQUIPMENT FOR THE SMALLER LABORATORY*

A. REEVES**

The technical problems faced by a motion picture processing laboratory are
fundamentally the same regardless of the size of the plant or its location. Meth-
ods that will produce first-quality results will do so whether they are applied
to a few thousand feet of film or to millions of feet of film per week.

The problem of applying these methods on a commercially profitable basis,
however, varies directly with the volume of film being handled. Installing such
modern methods as machine development of negative and positive film, accurate
sensitometric control, and the like, may be more complicated and expensive in
the case of a large plant; but once the installation of equipment and routine is
made, the investment speedily justifies itself.

In the smaller plant, that is not always the case. Unless the designing engi-
neer of such equipment takes into consideration the economic, as well as the
technical circumstances under which such a plant operates, the investment in
money and plant space involved in the installation is likely to bear an unprofit-
ably high ratio to the maximum potential savings attainable by using the modern
methods.

At the same time, the technical advantages of better and more uniform process-
ing, and the cash savings achieved through minimizing the footage spoiled by in-
correct processing, can be even more important in the smaller plant than in the
large one.

The large laboratory can count upon practically continuous operation through-
out the year; the smaller plant's operation is more generally intermittent. In
the large plant there is generally a more or less variable volume of negative de-
velopment and daily printing, counterbalanced by a fairly steady flow of release
printing. Further, such a plant will usually handle the output of several producing
units, or, as in the case of a commercial laboratory, that of several independent
units or studios.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
24, 1937.

** Art Reeves Motion Picture Equipment Co., Hollywood, Calif.
446

NEW MOTION PICTURE APPARATUS

447

In the smaller plant, on the other hand, the laboratory's activity is more gener-
ally keyed to the activity of one or two producing units with the possibility of
occasional commercial work. When the unit is in production, the plant's output
is chiefly negative development, with a minimum of daily print footage; when the
production is finished there is a varying amount of release print making. In
some cases this must be done on 16-mm. as well as on 35-mm. film.

To install the type of machinery used in a major laboratory in a plant oper-
ated under these conditions would be economically unsound. Suppose, for in-
stance, that developing machines were installed upon the same basis common in

FIG. 1. Complete developing machine installation (front view).

the large Hollywood plants, where one machine or battery of machines is used ex-
clusively for developing negative film, and a second machine or group of machines
exclusively for positive. In the large plant, both machines will be kept busy al-
most continually. In the average smaller plant outside such production centers
as Hollywood, New York, and London, one machine or the other would be stand-
ing idle, and therefore profitless, for long periods of time.

It is, of course, possible in several excellent machines to vary the developing
time sufficiently that the same machine can be used for developing either nega-
tive or positive film. Such machines, however, almost always require more
or less involved re-threading of the film webs, or draining and refilling the
developer tanks for the change, so they can not truly be called all-purpose ma-
chines in the commercial sense of the term.

448

NEW MOTION PICTURE APPARATUS tf. S. M. P. E

To meet this need, the developing machine described herein has been pro-
duced during the past year. It is definitely an all-purpose machine, being adapt-
able to developing negative or positive film without either re-threading the film-
web or re-filling the tanks. It will handle either 35-mm. or 16-mm. film inter-
changeably. It occupies the smallest amount of floor space possible without
unduly restricting either capacity or efficiency.

At the same time, the machine makes no compromise in the matter of quality.
It is engineered according to the most approved and modern standards. The
film is under a minimum of tension, driven by the rollers at the bottom of each
loop; no sprockets are used. The developing solutions are circulated continu-

, f t id** it**'******

tttti M til

FIG. 2. Negative development tank.

ously through a special manifold system that produces turbulation sufficient to
avoid directional markings. The temperature of all solutions is thermostatically
controlled, as is the temperature and humidity of the drying compartment. A
special pneumatic squeegee eliminates carrying over the solutions. All mate-
rials have been carefully chosen for their lack of chemical effect upon the solutions
used.

The tanks are of wooden construction. The framework for the machinery is
largely duralumin. All metal-work in contact with either solutions or film is
stainless steel, while generous use has been made of bakelite, celoron, and similar
non-corrosive plastics for such parts as film-carrying rollers, immersed driving
gears, circulating pumps, and the like. The solutions are circulated through
special hard-rubber tubing and flexible rubber piping.

Oct., 1937]

NEW MOTION PICTURE APPARATUS

449

The machine is shown in Fig. 1. In the standard installation, it occupies two
small rooms. The tank section shown in the foreground occupies one room,
which is safely darkened. The drying compartment, air-compressors, and motors
occupy the other room, which may be illuminated by normal white light. The
film passes from one room to the other in a metal tube passed through the wall.

There are seven compartments in the composite tank unit : positive developer

FIG. 3. Developing solution circulating systems.

tank, negative developer tank, rinse tank, hypo tank, wash tank, and two small
storage tanks for negative developer and positive developer, respectively.

The two storage tanks are at the outer end of the tank unit. Over them is the
light-tight feed magazine which carries the undeveloped film on a standard 2000-
f t. reel and is protected by an automatic alarm that warns of the approach of the
end of a reel.

Next comes the positive developing tank. Next to it is the negative developing
tank (Fig. 2). In both these sections of the machine, the film loop starts at the
left-hand side of the machine and crosses the tank in a thin horizontal spiral,
passing to the rinse tank from the right-hand end of the loop.

Both loops are kept threaded at all times. If, as seen in Fig. 2, positive film
is being developed, the leader in the negative tank is simply broken from the

450 NEW MOTION PICTURE APPARATUS [J. S. M. p. E.

strand and allowed to hang loosely in the tank, with the ends clipped to the
frame. As the film drive is from the bottom of the loop only, and in this in-
stance the loop hangs clear of the bottom driving rollers, the film in this tank does
not move.

When the machine is to be used for developing negative, the positive-tank
leader is similarly broken from the strand, and the ends of the negative loop re-
connected to the main strand with film clips.

Two separate systems are used to circulate the developing solutions (Fig. 3).
The negative developer circulating system is entirely independent of that used
to circulate the positive developer. Thus when the machine is in use only one of
the developer-circulating systems need be kept in operation.

In either case, the overflow from the developing tank feeds directly into the
appropriate storage tank. From the storage tank the solution passes through a
specially built centrifugal pump, constructed entirely of bakelite and celoron,
through external tubing of rubber to the bottom of the developing tank. Here
it is directed along one side of the narrow tank, from which it recoils with a whirl-
ing motion that imparts the necessary turbulation to the solution.

Each of the two circulating systems has its own independent temperature-control
system. A stainless steel encased electric heating unit is placed at the bottom
of each storage tank, and is connected in series to a three-positioned Mercoid
switch. Connected also to this switch may be an electric refrigerating unit, through
which the solution is pumped in stainless steel tubing. The thermostats auto-
matically hold the solution within a range of 3° of any predetermined tempera-
ture. The temperatures of the solutions in the developing tanks are indicated
by two separate thermometers mounted on the side of the tank assembly.

The film-moving mechanism is of the conventional type (Fig. 4). It is sup-
ported by a rigid duralumin frame which may be hoisted clear of the tanks.
All parts of this assembly that are immersed in the solutions are made of stain-
less steel, bakelite, or celoron.

The main driving shaft extends the full length of the tank unit, on the right-
hand side. At each film loop a gear-driven vertical shaft extends to the bottom
of the loop where, by means of bakelite bevel gears, it drives a stainless steel
shaft upon which are fixed the driving rollers. The film is under tension only
when the take-up brings it into contact with these powered rollers; otherwise it
moves freely on the free-rolling upper rollers.

As the film passes from each tank, it goes between a pair of bakelite nozzles
from which downward-slanting currents of air are directed against the faces of the
film. This results in a squeegeeing action that virtually eliminates carrying over
solutions from one tank to the other. There is therefore no dilution, and the
solutions have a considerably increased active life.

In the farther room, as has been stated, are the drying compartment, two sepa-
rate air-circulating systems, and the variable-speed film-moving drive. This
drive while using a constant-speed electric motor, acts like an infinitely variable
transmission and permits any variation in developing time between ls/4 minutes
and 18 minutes. The variation is controlled by a small controlling wheel placed
immediately below an indicating tachometer.

Two independent air-circulating systems are used: ' a high-pressure system for
the pneumatic squeegees, etc., and a low-pressure system for the film-drying

Oct., 1937]

NEW MOTION PICTURE APPARATUS

451

compartment. Both normally draw their air from the room in which the dry-box
end of the machine is located. The high-pressure system, driven by its own elec-
tric motor, uses a rotary compressor. An efficient air-cleaner is fitted to its
intake, and special non-back-pressure silencers are fitted to both the intake and
the exhaust lines, to minimize the noise of operation. A safety-valve is also fitted
to the exhaust line. This high -pressure air system is of sufficient capacity to take
care of the needs of two of these machines if necessary.

The low-pressure system draws its air through a large manifold fitted with two
large intake ports protected by interchangeable air-filters of spun glass impreg-

FIG. 4. Complete installation, showing film-moving mechanism and drying
cabinet (rear view).

nated with viscous oil. After filtering, the air passes a heater unit which warms
it to the desired temperature for drying the film. This heater has two degrees of
heating — the high setting drawing 10 kw. and the low 5 kw. Both are thermo-
statically controlled. When the machine is to be used in localities where ab-
normally high temperatures are to be encountered, an electric air-cooling unit
may also be fitted. A separate thermostat operates a warning bell in case of any
failure of either the air-circulating fan or the heater-units.

The fan forces 1000 cubic feet of air per minute into the film-drying compart-
ment. The air enters at the bottom of the compartment and is directed upward
by four adjustable deflecting vanes. A second thermostat guards the tempera-
ture of this drying compartment, holding it within a range of 3° of any predeter-
mined figure.

452 NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

The drying compartment is constructed along conventional lines. It is of sheet
metal, with two large glass-paned doors on either side. The film moves through
this compartment much as it does through the solution tanks, being carried on
bakelite rollers. Only the lower rollers are driven, while the upper rollers revolve
freely on ball bearings. In the middle of each film loop in this compartment is a
large cloth-covered drum which revolves freely and serves to polish the celluloid
surface of the film.

The usual vapor-proof lamps illuminate the inside of the drying cabinet and
facilitate inspection of the film as it dries.

Emerging from the drying compartment, the film is taken up on a standard
2000-ft. reel, driven by an equalized belt drive.

In every possible respect, a high factor of safety has been provided in the
machine. The power units, heating units, compressors, solution pumps, and
the like, are generously over-sized. The film-moving drive, for instance, actually
requires only Vio hp. for normal operation, yet a 1/4-hp. motor is used. In the
same way, the undeveloped film is fed from a standard 2000-ft. reel, requiring
that the film be rewound to reveal any breaks or tears that may have been occa-
sioned in the camera.

A similar equipment problem is encountered in the matter of applying the
accuracy of sensitometric control to the routine of laboratory operations. The
majority of standard sensitometers are built with such involved care for every de-
tail that could possibly affect their accuracy that they are prohibitively expensive
for the average laboratory. In the large film centers this is to some extent offset
by the excellent service maintained by the raw-film manufacturers, who make
sensitometric strips for the laboratories using their products. But elsewhere the
average laboratory — in which sensitometric control is more likely to be needed — is
too remotely located to take advantage of this service, and not financially able to
purchase a standard sensitometer.

To meet this need, the Artreeves Sensitester has been developed. This is a
simple, accurate light-test machine that may be converted into a practical sensi-
tometer by moving a single control.

The Sensitester is shown in (Fig. 5). Essentially it consists of a supporting
stand, a light-metering assembly, and mechanisms to carry and move the film
being tested and that upon which the test is made.

When used as a film light-tester, the negative to be tested is threaded from one
rewind to the other, across the light-metering assembly. The positive film upon
which the light-test is to be printed is threaded from the feed magazine, over a
sprocket and under a pressure-pad or platen, past another sprocket and into the
take-up magazine. For the sake of safety, these magazines are fully enclosed,
to minimize the possibility of the film's being fogged through prolonged exposure
to the "safe" light of the testing room.

When making a test, the horizontal bar extending across the front of the ma-
chine is depressed. This lowers the platen and magazine assembly, bringing the
two films into contact across the exposure plane. At this moment, the expo-
sure is made automatically. As the control bar is raised, the exposed section of
positive film is automatically wound into the take-up magazine and replaced by a
fresh section for the next test.

The light is metered through a series of adjustable diagragms that may be

Oct., 1937]

NEW MOTION PICTURE APPARATUS

453

pre-set to coordinate with the characteristics of the printer used, giving eleven
graduated exposure-steps corresponding to printer-lights 1 to 21. In addition to
printing these light-test frames from the picture area of the negative, the machine
also prints the marginal footage-numbers, eliminating any change of confusion in
regard to similar "takes."

Timing the exposure is accurately controlled by an adaptation of the metronome
principle. A counterweighted pendulum arm is used, the position of one of the

FIG. 5. The Sensitester.

weights being adjustable. This controls the time of the pendulum's swing. As
the platen is brought down to make the exposure, the metronome arm is auto-
matically released : as it starts its travel, it switches on the exposing light ; as it
finishes its return stroke, it switches off the light, and is itself locked into place
ready for the next test.

Combining these two principles of proved accuracy for this purpose makes it
possible to utilize the same machine as a practicable sensitometer. Since the
metronome principle gauges the exposure, no outside factor can alter this timing.
Since the light for all steps comes from a single source at one exposure and is
metered through a fixed series of diaphragms, the relative exposures of the various
steps can not be disturbed.

454 NEW MOTION PICTURE APPARATUS

Therefore a supplementary series of fixed diaphragms is built into the machine.
Each of these diaphragms admits light in a fixed, logarithmically progressing
ratio. When making sensitometric strips on negative film, a supplementary
filter may be fitted to match the light to daylight standards.

The resulting sensitometric strip contains only half as many gradations as
those made on a standard sensitometer ; but the strips have been made to match
identically the alternate steps of standard sensitometric strips. For the practical
purposes of the average laboratory, these strips have been found to serve quite
as well as the standard type. It is obvious that since the gamma is a function
primarily of the straight-line portion of the H&D curve, which may be plotted
equally well from less closely spaced points, the gamma may be determined from
these simpler strips with equal accuracy.

This design has been engineered so that it will maintain its fundamental ac-
curacy regardless of external conditions. Variations in current supply, for ex-
ample, while affecting the overall result, can not upset the relation between the
individual exposure-steps, since all are made at a single exposure, from a common
light-source, with the gradations produced by metering the light optically. Such
fluctuations can not affect the timing, since this is not done by motors, but by the
uniformity of metronome control.

From the viewpoint of practical laboratory operation, this machine is doubly
advantageous. In addition to the lowered equipment cost obviously gained by
combining two instruments into one, there is the further advantage of making it
possible to utilize more frequently the advantages of sensitometric control as a
routine check on the accuracy of laboratory operations. Separate machines
might not be used so frequently in routine operations, but with the two instru-
ments in one unit, accurate sensitometric strips can be made as easily and as fre-
quently as ordinary light-tests.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D.C.,
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

American Cinematographer

18 (Aug., 1937), No. 8

New Film Editing Aid Gives Larger Picture (p. 318).
How One Cinematographer Secures Variable Diffusion
(p. 328). T. SPARKUHL

Filmtechnik

13 (July 6, 1937), No. 11

Bedingungen fur gute Bild-und Tonwiedergabe (Re-
quirements for Good Projection and Good Sound
Reproduction) (p. 118). E. KAMMERER

Entwicklung der Hochfrequenzkinematografie (Evolu-
tion of High-Speed Motion Pictures) (p. 121). F. E. v. ECKARD

Lichtpolarisatoren beim Raum- und Mehrfarbenbild-
wurf (Use of Polarizers for Stereoscopic and Color
Projection) (p. 123). O. BENDER

International Projectionist

12 (July, 1937), No. 7
The Neon Tube Oscilloscope as a Precision Servicing

Instrument (p. 18). T. P. HOVER

Typical Troubles in Modern Sound Reproducing Units —

II (p. 22). LE R. CHADBOURNE

Motion Picture Herald (Better Theatres Section)

128 (July 24, 1937), No. 4
Theater Acoustics Today (p. 39). C. C. POTWIN

Photographische Industrie

35 (July 21, 1937), No. 29

Neues iiber ein Kino-Aufnahmeobjektiv mit verander-
licher Brennweite (Announcement about a Motion
Picture Lens Having a Changeable Focal Length)
(p. 793).

455

456 CURRENT LITERATURE

Radio Engineering

17 (July, 1937), No. 7
Plate Efficiency of Class "B" Amplifiers (p. 14). P. ADORJAN

RCA Review

11 (July, 1937), No. 1
Television Studio Design (p. 14). R. M. MORRIS AND

R. E. SHELBY
Television Transmitter Operating at High Powers and

Ultra-High Frequencies (p. 30). J. W. CONKLIN AND

H. E. GIHRING

"Batalum," a Batium Getter for Metal Tubes (p. 117). E. A. LEDERER AND

D. H. WAMSLEY

La technique cinematographique

9 (June, 1937), No. 78
L'Emulsion Cinematographique et Son Emploi (Motion

Picture Emulsion and Its Applications) (p. 950). A. P. RICHARD

Une Belle Projection en Couleurs en 16-Mm. (Good

16-Mm. Color Projection) (p. 955). G. VIEL

Television

10 (Aug., 1937), No. 114

Television Projection with the Cathode-Ray Tube
(p. 457).

FALL, 1937, CONVENTION

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA, NEW YORK
OCTOBER llth-14th, INCLUSIVE

Officers and Committees in Charge

W. C. KUNZMANN, Convention Vice-President

J. I. CRABTREE, Editorial Vice-President

S. K. WOLF, President

G. FRIEDL, Jr., Chairman, Atlantic Coast Section

PAPERS

G. E. MATTHEWS, Chairman

C. N. BATSEL M. E. GILLETTE E. C. RICHARDSON

L. N. BUSCH E. W. KELLOGG F. H. RICHARDSON

O. O. CECCARINI W. A. MACNAIR P. R. VON SCHROTT

A. A. COOK R. F. MITCHELL H. C. SILENT

L. J. J. DIDIEE W. A. MUELLER H. G. TASKER

C. FLANNAGAN I. D. WRATTEN

Local Arrangements and Reception Committee

G. FRIEDL, JR., Chairman

O. M. GLUNT A. S. DICKINSON E. A. WILLIFORD

H. B. SANTEE M. C. BATSEL E. G. HINES

A. N. GOLDSMITH H. RUBIN V. B. SEASE

L. W. DAVEE J. FRANK, JR. D. E. HYNDMAN

E. I. SPONABLE O. F. NEU J. A. NORLING

Registration and Information

W. C. KUNZMANN, Chairman
E. R. GEIB S. HARRIS F. HOHMEISTER

Ladies' Reception Committee

MRS. S. K. WOLF and MRS. O. F. NEU, Hostesses

MRS. O. M. GLUNT MRS. T. E. SHEA MRS. A. S. DICKINSON

MRS. H. GRIFFIN MRS. J. FRANK, JR. MRS. E. A. WILLIFORD

MRS. E. I. SPONABLE MRS. G. FRIEDL, JR. MRS. M. C. BATSEL

MRS. D. E. HYNDMAN

Banquet Committee

A. S. DICKINSON, Chairman

O. M. GLUNT W. C. KUNZMANN H. GRIFFIN

J. H. SPRAY S. HARRIS O. F. NEU

G. FRIEDL, JR. M. C. BATSEL H. B. SANTEE

457

458 FALL CONVENTION [J. S. M. P. E.

Publicity Committee

W. WHITMORE, Chairman

J. J. FINN G. E. MATTHEWS F. H. RICHARDSON

J. R. CAMERON S. HARRIS P. A. McGuiRE

Projection Committee

H. GRIFFIN, Chairman

H. RUBIN F. E. CAHILL, JR. G. C. EDWARDS

J. O. BAKER M. D. O'BRIEN A. L. RAVEN

P. D. RIES J. S. WARD C. F. HORSTMAN

J. FRANK, JR. C. R. WOOD

Officers and Members of New York Projectionists Local 306. I. A. T. S. E.

Membership Committee

E. R. GEIB, Chairman

S. HARRIS A. A. COOK J. A. MILLER

J. A. HAMMOND J. K. ELDERKIN J. R. MANHEIMER

Headquarters

The headquarters of the Convention will be the Pennsylvania Hotel, where ex-
cellent accommodations have been assured and a reception suite will be provided
for the Ladies' Committee. An excellent program of entertainment will be ar-
ranged by the hostesses.

Special hotel rates guaranteed to SMPE delegates, European plan, will be
as follows:

One person, room and bath $3 . 50

Two persons, double bed and bath 5 . 00

Two persons, twin beds and bath 6 . 00

Parlor suite, one person 11 .00 up

Parlor suite, two persons 13. 00 up

Everyone who plans to attend the Convention should return his reservation card
to the Hotel promptly in order to be assured of satisfactory accommodations.
Consult your local railroad ticket agent with regard to coach and pullman rates.

Parking accommodations will be available to those who motor to the Conven-
tion at the fire-proof garage of the Hotel, at the rate of $1.25 for twenty-four hours
or $1.00 for twelve hours, including pick-up and delivery at the door of the Hotel;
weekly rate, $7.50.

Registration

Registration headquarters will be located on the eighteenth floor of the Hotel at
the entrance of the Salle Moderne, where the technical sessions will be held. Ex-
press elevators from the lobby will be reserved for the Convention. All members
and guests attending the Convention are expected to register and receive their
badges and identification cards required for admission to certain evening sessions
of the Convention, as well as to the Radio City Music Hall, Paramount Theater,
Warner Bros. Strand Theater, and the Roxy Theater, which will hpnor the cards
as courtesy admissions.

Oct., 1937] FALL CONVENTION 459

Luncheon and Banquet

The usual informal get-together luncheon will be held at noon on October llth
in the Roof Garden of the Hotel, and the semi-annual banquet and dance will
take place on the evening of October 13th.

Addresses will be delivered by prominent members of the industry on both
occasions. At the banquet the annual presentation of the SMPE Progress Medal
and the Journal Award will be made, and the officers-elect for 1938 will be intro-
duced. The banquet will conclude with dancing and entertainment.

Tickets for admission to the informal luncheon and the banquet may be ob-
tained at the registration desk. Banquet tables reserved for 8, 10, and 12 per-
sons.

Points of Interest

Headquarters and important branch offices of practically all the important firms
engaged in producing, processing, and exhibiting motion pictures and in manu-
facturing equipment therefor, are located in metropolitan New York. Although
no special trips or tours have been arranged to any of these plants, the Conven-
tion provides opportunity for delegates to visit those establishments to which they
have entree. Among the points of interest to the general sightseer in New York
may be listed the following:

Metropolitan Museum of Art.— Fifth Ave. at 82nd St.; open 10 A.M. to 5 P.M.
One of the finest museums in the world, embracing practically all the arts.

American Museum of Natural History. — 72nd St. between Columbus Ave. and
Central Park West ; 9 A.M. to 5 P.M.

New York Museum of Science and Industry. — RCA Building, Rockefeller Cen-
ter; 10 A.M. to 5 P.M. Exhibits illustrate the development of basic industries,
arranged in divisions under the headings food, industries, clothing, transportation,
communications, etc.

Museum of the American Indian. — -Broadway and 155th St., 2 P.M. to 5 P.M.

Hayden Planelarium. — Central Park West at 77th St. Performances at 11 A.M.,
2 P.M., 3 P.M., 4 P.M., 8 P.M., and 9 P.M. Each presentation lasts about
45 minutes and is accompanied by a lecture on astronomy.

Rockefeller Center. — 49th to 51st Sts., between 5th and 6th Aves. A group of
buildings including Radio City Music Hall, the Center Theater, the RCA Building,
and the headquarters of the National Broadcasting Company, in addition to
other interesting general and architectural features.

Empire State Building. — The tallest building in the world, 102 stories or 1250
feet high. Fifth Ave. at 34th St. A visit to the tower at the top of the building
affords a magnificient view of the entire metropolitan area.

Central Park. — 59th to 110th Sts., Central Park West to Fifth Ave. Here are
located the Metropolitan Museum of Art, and a number of other general and
educational features including the zoological garden and "Cleopatra's Needle."
The latter is an Egyptian obelisk presented to the City in 1879 by the Khedive of
Egypt.

Greenwich Village. — New York's Bohemia; a study in contrasts. Here are
located artists and artisans, some of the finest homes and apartments, and some
of the poorest tenements.

Holland Tunnel. — The first vehicular tunnel constructed beneath the Hudson

460 FALL CONVENTION

River; at Canal St., connecting New York with New Jersey; more than 9000
feet long.

Foreign Districts.— Certain sections of the city are inhabited by large groups of
foreign-born peoples. There is the Spanish section, north of Central Park; the
Italian district near Greenwich Village; Harlem, practically a city in itself, num-
bering 300,000 negroes; Chinatown, in downtown Manhattan; the Ghetto, the
Jewish district; and several other such sections.

Miscellaneous. — Many other points of interest might be cited, but space permits
only mentioning their names. Directions for visiting these places may be obtained
at the Convention registration desk: Pennsylvania Station, Madison Square,
Union Square, City Hall, Aquarium and Bowling Green, Battery Park, Washing-
ton Square, Riverside Drive, Park Avenue, Fifth Avenue shopping district, Grand
Central Station, Bronx Zoo, St. Patrick's Cathedral, St. Paul's Chapel, Cathedral
of St. John the Divine, Trinity Church, Little Church Around the Corner, Wall
St. and the financial district, Museum of Natural History, Columbia University,
New York University, George Washington Bridge, Brooklyn Bridge, Triborough
Bridge, and Statue of Liberty.

Steamships. — The S. S. Normandie will be in dock open for inspection, on Octo-
ber 12th, pier 88 at the foot of West 48th St. ; tickets on sale at the pier, 50|< each.

TENTATIVE PROGRAM
MONDAY, OCTOBER llth

9:00 a. m. Salle Moderne; Registration.

10:00 a. m.
to 12:00 p. m. Salle Moderne; Business and General Session.

Opening Remarks by President S. K. Wolf (10 Min.)

Report of the Convention Committee; W. C. Kunzmann,
Convention Vice-President (5 Min.)

Report of the Membership Committee; E. R. Geib, Chairman
(5 Min.)

Society Business; Election of Officers and Other Business
(20 Min.)

"Hunting with a Microphone the Songs of Vanishing Birds;"
P. Kellogg, Laboratory of Ornithology, Cornell University,
Ithaca, N. Y. (Demonstration.) (30 Min.)

"Safeguarding and Developing Our Film Markets Abroad;"
N. D. Golden, Motion Picture Division, U. S. Department
of Commerce, Washington, D. C. (20 Min.)

"High-Speed Motion Picture Photography Applied to the
Design of Telephone Apparatus;" W. Herriott, Bell Tele-
phone Laboratories, Inc., New York, N. Y. (Demonstra-
tion.) (20 Min.)
12:30 p. m. Roof Garden; Informal Luncheon.

For members, their families, and friends.

Address by Mr. Louis Nizer, Secretary, New York Film Board
of Trade, New York, N. Y.

Address by Mr. Martin Quigley, President, Quigley Publishing
Co., Inc., New York, N. Y. : "Propaganda, Education, and
the Entertainment Film."
2:00 p. m.
to 5:00 p. m. Salle Moderne; Photographic and Laboratory Session.

"Further Progress in Film Storage;" Capt. J. G. Bradley,
National Archives, Washington, D. C. (20 Min.)

"The Effect of the Composition of an MQ Developer on Its
Reduction Potential;" R. M. Evans and W. T. Hanson, Jr.,
Kodak Research Laboratories, Rochester, N. Y. (20 Min.)

"A Modern Motion Picture Laboratory;" C. L. Loot ens, Re-
public Productions, Inc., North Hollywood, Calif. (20
Min.)

"Grain-Size Determination and Other Applications of the
Callier Effect;" J. Eggert and A. Kiister, I. G. Farbenindus-
trie Film Fabrik, Wolfen, Germany. (15 Min.)

461

462 FALL CONVENTION [J. S. M. P. E.

"Demonstration of Three-Dimensional Motion Pictures;"
G. W. Wheelwright, 3d, Land-Wheelwright Laboratories,
Boston, Mass. (1 Hour)
8:00 p. m.

to 10:30 p. m. Auditorium, Bell Telephone Laboratories; Special Sound Ses-
sion.

"Distortion in the Reproduction of Hill-and-Dale Records;"
M. J. Di Toro, Thomas A. Edison, Inc., Orange, N. J. (20
Min.)

"Recent Developments in Hill-and-Dale Recorders;" L. Vieth
and C. F. Wiebusch, Bell Telephone Laboratories, Inc.,
York, N. Y. (Demonstration.) (20 Min.)

"Nomenclature and Specifications Including Description of the
Various Types of Movietone Release;" J. K. Hilliard, Metro-
Goldwyn-Mayer Studios, Culver City, Calif. (Demonstra-
tion.) (25 Min.)

"Film Perforation and 96-Cycle Frequency Modulation in
Sound-Film Records;" J. Crabtree and W. Herriott, Bell
Telephone Laboratories, Inc., New York, N. Y. (15 Min.)

"Push-Pull Recording;" J. G. Frayne and H. C. Silent, Elec-
trical Research Products, Inc., Hollywood, Calif. (25 Min.)

"Stereophonic Recording and Reproduction from Motion Pic-
ture Film Records;" Introductory remarks by J. P. Max-
field, Electrical Research Products, Inc., New York, N. Y.
(Demonstration.) (15 Min.)

TUESDAY, OCTOBER 12th

10:00 a. m.
to 12:30 p. m. Salle Moderne; Engineering Practice Session.

"Air-Conditioning with Lithium Chloride;" G. A. Kelley,
Surface Combustion Corp., Toledo, Ohio. (20 Min.)

"The Activated Alumina System as Applied to Air-Condition-
ing and Drying Problems;" G. L. Simpson, Pittsburgh
Lectrodryer Corp., Pittsburgh, Pa. (20 Min.)

"Die Castings and Their Application to Photographic Appli-
ances;" C. Pack, Doehler Die Casting Co., New York, N. Y.
(20 Min.)

"The Use of Inconel for Photographic Film Processing Equip-
ment;" G. L. Cox, International Nickel Co., Inc., New York,
N. Y. (20 Min.)

"Newer Types of Stainless Steel and Their Applications to
Photographic Processing Equipment;" H. A. Smith, Re-
public Steel Corp., Massilon, Ohio. (15 Min.)

"Vacuum-Tube Engineering for Motion Pictures;" L. C. Hol-
lands and A. M. Glover, RCA Manufacturing Co., Inc.,
Harrison, N. J. (25 Min.)
2 :00 p. m.
to 5:00 p. m. Salle Moderne; Lighting and Studio Session.

Oct., 1937] FALL CONVENTION 463

"Spectral Distribution and Color-Temperature of the Radiant
Energy from Carbon Arcs Used in the Motion Picture Indus-
try;" F. T. Bowditch and A. C. Downes, National Carbon
Co., Inc., Cleveland, Ohio. (20 Min.)

"Recent Developments in Background Projection;" G. G.
Popovici, J. G. Saltzman, Inc., New York, N. Y. (20 Min.)

"Recent Developments in Gaseous Discharge Lamps;"
S. Dushman, Research Laboratory, General Electric Co.,
Schenectady, N. Y. (20 Min.)

Report of the Studio Lighting Committee, R. E. Farnham,
Chairman. (20 Min.)

"Light Control in Photography;" G. Mili, Westinghouse Elec-
tric & Manufacturing Co., Bloomfield, N. J. (20 Min.)

"Modulated High-Frequency Recording as a Means of Deter-
mining Conditions for Optimal Processing;" J. O. Baker
and D. H. Robinson, RCA Manufacturing Co., Inc., Cam-
den, N. J. (20 Min.)

"Recording Tests on Some Recent High-Resolution Experi-
mental Emulsions;" J. O. Baker, RCA Manufacturing Co.,
Inc., Camden, N. J. (20 Min.)
8:00 p. m.
to 11:30 p. m. Salle Moderne.

Showing of selected historical motion pictures arranged by
John E. Abbott, Director of the Film Library, The Museum
of Modern Art, New York, N. Y.

Showing of a recent feature picture and shorts.

WEDNESDAY, OCTOBER 13th

10:00 a. m.

to 12:30 p. m. Salle Moderne; Projection Practice Session, A. N. Goldsmith,
Chairman.

"The Practice of Projection;" A. N. Goldsmith, New York,
N. Y. (5 Min,)

"Grading Projectionists;" G. P. Barber, Government of the
Province of Alberta, Edmonton, Alberta, Canada. (20
Min.)

"Cooperation as the Keynote of Successful Small-Town Projec-
tion;" T. P. Hover, Warner's Ohio Theater, Lima, Ohio.
(15 Min.)

"A Discussion of Screen Image Dimensions;" F. H. Richard-
son, Quigley Publishing Co., Inc., New York, N. Y. (15
Min.)

"New Approaches to the Presentation of the Motion Picture
Theater;" B. Schlanger, New York, N. Y. (15 Min.)

"Precision All-Metal Reflectors for Use with Projection Arcs;"
C. E. Shultz, Heyer-Shultz, Inc. Montclair, N. J. (Demon-
stration) ,(15 Min.)

464 FALL CONVENTION [J. S. M. P. E.

"Perforated Screens and Their Faults;" F. H. Richardson,
Quigley Publishing Co., Inc., New York, N. Y. (10 Min.)

"Commercial 16-Mm. Projection Faults;" C. L. Greene, Min-
neapolis, Minn. (15 Min.)

2:00 p. m. Open Afternoon

7:30 p. m. Salle Moderne; Semi- Annual Banquet.

Short addresses by eminent members of the industry; names to

be announced later.
Presentation of annual SMPE Progress Medal and Journal

Awards.
Entertainment and Dancing.

THURSDAY, OCTOBER 14th

10:00 a. m.

to 12:00 p. m. Salle Moderne; Apparatus Symposium and Manufacturers'
Announcements.

"The Sound-Level Meter in the Motion Picture Industry;"
H. H. Scott, General Radio Co., Cambridge, Mass. (15
Min.)

"A New Motion Picture Camera Crane;" E. H. Heyer and
E. L. Fischer, Universal Pictures Corp., Universal City, Calif.
(15 Min.)

"Non-Intermittent Projection;" J. F. Leventhal, Leventhal
Patents, Inc., New York, N. Y. (15 Min.)

"New Ideas in Mobile Sound Recording Equipment;" C. M.
Ralph and J. G. Matthews, General Service Studios, Holly-
wood, Calif. (15 Min.)

"A Mobile Sound Recording Channel;" L. T. Goldsmith,
Warner Brothers Pictures, Inc., Burbank, Calif. (15 Min.)

"A Device for Cleaning the Sound- Track of Motion Picture
Film during Projection;" R. V. Fisher, Flower City Speci-
alty Co., Rochester, N. Y. (Demonstration.) (15 Min.)

"A Recorder for Making Buzz-Tracks;" E. W. Kellogg, RCA
Manufacturing Co., Inc., Camden, N. J. (10 Min.)

"Advantages of Spark Illumination in Certain Types of Photog-
raphy;" M. A. Durand, International Filmbook Corp.,
South Norwalk, Conn. (20 Min.)

"A Flash Fire Valve for Fire Prevention in Motion Picture
Projectors;" R. V. Fisher, Rochester, N. Y. (20 Min.)

2:00 p. m.
to 5:00 p. m. Salle Moderne; Sound Session.

"Reduction of Loop-Length Variations in Non-Slip Printers;"
E. W. Kellogg, RCA Manufacturing Co., Inc., Camden,
N. J. (20 Min.)
"Transmission Characteristics of Western Electric Re-Recording

Oct., 1937] FALL CONVENTION 465

Channels;" C. R. Daily and F. L. Hopper, Electrical Re-
search Products, Inc., Hollywood, Calif. (20 Min.)

"Permanent Magnet 4-Ribbon Valve for Portable Channel
Push-Pull Recording;" E. C. Manderfeld, Electrical Re-
search Products, Inc., Hollywood, Calif. (20 Min.)

"Improvements in Noise-Reduction Circuits;" R. R. Scoville,
Electrical Research Products, Inc., Hollywood, Calif. (20
Min.)

"Improved Methods of Detecting Light-Valve Overload;"
C. R. Daily, Electrical Research Products, Inc., Hollywood,
Calif. (20 Min.)

"Overload Limiter for the Protection of Modulating Devices;"
R. R. Scoville, Electrical Research Products, Inc., Holly-
wood, Calif. (20 Min.)

W. C. KUNZMANN, Convention Vice-President

J. I. CRABTREE, Editorial Vice- President

G. E. MATTHEWS, Chairman, Papers Committee

This is a tentative program and, as such, is subject to change. The Society is not
responsible for statements made by authors.

SOCIETY ANNOUNCEMENTS

FALL CONVENTION

Full details concerning the Fall Convention to be held at the Hotel Pennsyl-
vania, New York, N. Y., October llth to 14th, together with the preliminary
papers program, are contained hi the preceding section of this JOURNAL.

A meeting of the Board of Governors will be held on October 10th at the
Hotel Pennsylvania, at which time, in addition to usual administrative and
financial matters, the final details of the Convention will be completed.

ATLANTIC COAST SECTION

At the first meeting of the season, held at the Hotel Pennsylvania, New York,
N. Y., on September 15th, Mr. J. L. Forrest, of the Agfa Ansco Corp., Bingham-
ton, N. Y., presented a paper describing the new Agfacolor process.

The meeting was very well attended and considerable discussion followed the
presentation, which was accompanied by examples of the Agfacolor process in
slide-film form.

ADMISSIONS COMMITTEE

At a recent meeting of the Admissions Committee at the General Office of the
Society, the following applicants for membership were admitted to the Associate
grade:

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SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA

NEW YORK, N. Y.

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX NOVEMBER, 1937 Number 5

CONTENTS

Page

Some Lighting Problems in Color Cinematography

T. T. BAKER 471

Effect of Uneven Slit Illumination upon Distortion in Several

Types of Variable-Width Records

C. N. BATSEL AND C. H. CARTWRIGHT 476

The Organisation and Activities of the Research Council of the

Academy of Motion Picture Arts and Sciences

WILLIAM KOENIG 484

A Linear Decibel-Scale Volume Indicator F. G. Albin 489

Distortion in the Reproduction of Hill-and-Dale Recording. . . .
M. J. Di TORO 493

The Objective Quantitative Determination of the Graininess of
Photographic Emulsions A. GOETZ AND W. O. GOULD 510

New Motion Picture Apparatus
A Sound Kodascope E. C. Fritts and O. Sandvik 539

Current Literature 548

Fall, 1937, Convention at New York, N. Y., October, llth
to 14th

Highlights of the Convention 550

Final Program 555

Abstracts of Papers and Presentations 559

Society Announcements 573

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS, EDITOR

Board of Editors
J. I. CRABTREE, Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum ; to members, $5.00 per annum,
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
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Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers in question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 100 E. 42nd St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 180 Varick St., New York, N. Y.
Convention Vice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK, JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York, N. Y.

GOVERNORS

M. C. BATSEL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 25 Hunter Ave., Fanwood, N. J.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE. 205 W. Wacker Drive, Chicago, 111.

SOME LIGHTING PROBLEMS IN COLOR
CINEMATOGRAPHY*

T. T. BAKER**

Summary. — In additive processes the primaries are generally blue-violet, green,
orange spectral bands, -which are not narrow and overlap to some extent. The ex-
posure latitude of a color-screen process is less then that of black-and-white negative
stock. Underexposures often tend toward excessive blue, and overexposures toward
some other predominant color, due in some measure to differences in the foot and
shoulder of the characteristic curves of the emulsion when exposed to the three primary
bands.

Overexposure results in dilution of the colors, due to invasion of each primary into
its neighbor's territory. There is thus a color-saturation latitude in the screen or
matrix, distinct from a true emulsion latitude. The object here is to discuss a method
of calculating the approximate range of studio light-intensity that will preserve the
best color balance of which any particular additive process may be capable.

For Dufaycolor film, a wedge spectrogram of suitable steepness is made representing
average exposure, such as from a density of 0 to 2.5. Upon development and reversal,
the peaks throughout the wedge spectrum are shown as completely saturated (i. e., 100
per cent of the reseau or matrix saturation). But as any spectral zone is followed
downward from the peak, the color becomes diluted and may become even white as the
image approaches the base line, and, therefore, maximum exposure.

This is caused by the fact that, upon overexposure, scattering carries the light behind
(say) a green element into the region of neighboring blue and red elements, so that the
resulting color is reseau-green plus some blue and red, or reseau-green plus white.
The effect is accentuated in reseau composed of less saturated color elements. By
measuring from the peak to the position on any ordinate where distinct dilution be-
comes apparent, the permissible range of light-intensity on the set can be computed
from the difference of the log opacities of the two points on the ordinate.

This paper relates to problems connected with the lighting range of
the studios where additive systems of photography are employed.
Additive systems depend upon the use of three primary elements. In
the case of screen processes, these elements are of microscopic area in
motion picture film stock. In the case of the lenticular process, three
primary filters only are used of considerable area, in the camera and
projector. In all cases, however, it is generally agreed that the filters

*Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
19, 1937.

** Dufaycolor Research Laboratories, New York, N. Y.

471

472 T. T. BAKER [J. S. M. P. E.

employed transmit three spectral bands that overlap considerably,
somewhat on the lines of the three visual sensation curves as deter-
mined by Abney, Vierordt, Koenig, and others. The shape of the
transmission curves of the niters involves a peak usually in the neigh-
borhood of the dominant hue and tapers off in such a way as to over-
lap its neighbors to a more or less extent. Taking the green filter, for
example, minimum exposure would give an image using the peak of
the transmission curve, while for an overexposure the transmission
would encroach upon the adjacent areas of the blue and the red niters,
the extent of encroachment increasing with increasing overexposure.
The effect of overexposure is therefore tantamount to dilution of the
primary color, since green, for example, upon overexposure will be-
come green plus some blue and some red, making a total of green plus
some white; in other words, a diluted green.

There appear to be two kinds of latitude that require consideration
in the use of an additive color process. One is the latitude derived
from the characteristic curve of the emulsion ; the other is a latitude
in color saturation, dependent chiefly upon the degree of overlap of
the three primary elements. In other words, there is a color-satura-
tion latitude, dependent upon the transmissions of the screen elements,
as distinct from a true emulsion latitude. These can be to some ex-
tent correlated and a compensation made.

In photographing a subject in which there is ample color contrast
and the colors are reasonably saturated, perfectly flat lighting can
give an entirely satisfactory result. The color contrasts will provide
brilliance. If the subject be illuminated by a number of lamps in
various positions, so that a large range of light-intensity is included,
color dilution can easily step in and affect local and even overall
fidelity. If, on the other hand, the total range of light-intensity falling
upon any given object in the set be kept within a range that can be
computed from a wedge spectrogram in color of the color stock, then
the color rendering of the brightest and least illuminated parts of the
object will both be truly recorded. The apparatus used is an ordi-
nary diffraction-grating spectrograph, with a neutral gray wedge hav-
ing a density range of 0 to 2.5 in front of the slot behind which the film
is exposed. The light-intensity range of the wedge is thus 100 per
cent at base line to 0.4 per cent at the top of the wedge.

The "normal" exposure for the spectrogram has been taken as that
giving a density of 1.0 in the most exposed portion, in standard devel-
opment time in the Dufaycolor negative developer :

Nov., 1937]

LIGHTING IN COLOR CINEMATOGRAPHY

473

Metol

Sodium Sulfite (dry)
Sodium Thiosulfate
Sodium Silicate
Water to make

Caustic Soda
Water to make

10 grams
25 grams
25 grams
10 cc.
1000 cc.

10 grams
1000 cc.

Equal parts are mixed for use, and 3 minutes of development is given
at65°F.

For testing Dufaycolor stock the film is exposed through the matrix
or reseau, and developed as a negative, so that the wedge spectrogram
appears in complementary colors. It is then also developed and re-
versed, giving a natural-color
spectrum. In a print from a
normal negative, or in a reversal
print, the peaks throughout the
spectrum will appear of saturated
color — that is, as saturated as
the reseau primaries will permit,
degraded with black, as the
wedge steepens ; while as one fol-
lows any spectral band from the
peak to the base, the color be-
comes more and more pure — that
is, less degraded with black, and
would in an ideal case still be
pure at the base line, i. e., over
the whole light range of the
wedge, in this case 1:250. It
will be found in general, how-
ever, that the color becomes
diluted and may even appear almost white before the point of
maximum exposure has been reached on the base line. But it is
not difficult to find by visual inspection the range at any particular
spectral position over which the color appears undiluted, and by
simply measuring this length and converting it into terms of light-
intensity range, the limits of intensity can be ascertained.

That the change in color at each end of the light-intensity range is
not due to a gamma wavelength effect at the foot and shoulder of the

FIG. 1. Characteristic curves of
Dufaycolor motion picture negative
film exposed through blue, green, and
red filters, showing similarity in gen-
eral shape.

474

T. T. BAKER

[J. S. M. P. E.

characteristic curve may be seen from Fig. 1, where the Duf ay color
negative material is shown exposed behind three standard trichro-
matic filters.

A simple experiment to show the failure of an additive photo-
graphic material to retain color fidelity over too long a range of light-
intensity was made by photographing colored cards three feet long
and nine inches wide, illuminated by a 100-watt tungsten lamp placed
four inches from one extreme side. The rate at which the light tailed
off was measured by the inverse square law. Within the light-inten-
sity range of approximately 12.5 to 1 the color remains accurate and
is in good agreement with that obtained from the wedge spectrogram.

400

FIG. 2.

490 500 560 M>0 650

Transmissions of reseau elements of normal Dufaycolor
motion picture stock.

This range is dependent to some extent upon the saturation of the
reseau or matrix primaries. The standard material has transmissions
as shown in Fig. 2.

It was demonstrated by means of lantern-slides that full color satur-
ation was maintained over a longer range of light-intensity in the case
of a reseau composed of saturated colors, while the range was consid-
erably shortened in the case of an experimental reseau made with
very dilute primary colors. Color fidelity (as regards saturation)
was thereby shown to depend, in an additive process, upon the "color
latitude" given by the degree of saturation of the three elements, quite
apart from the color characteristics.

At this point in the presentation of the paper, a short piece of motion picture film
was projected, showing a small studio set lighted by white flame arcs so arranged that

Nov., 1937] LIGHTING IN COLOR CINEMATOGRAPHY 475

the intensities of the light falling upon the two sides of the set, as measured by re-
flection from the disk of a photometer, were identical; in other words, the range of in-
tensity was 1:1. Another shot followed, in which the lamps were so arranged as to
change the intensity to 5:1; and in a third shot to 25:1.

The general satisfactoriness of all three shots indicates that color
fidelity is unbalanced only when the light-intensity varies greatly at
contiguous spots, such as the side and front of an artist's face lighted
by oblique illumination or by too intense spotlighting.

Many photographers complain that they are unable in natural-
color photography to employ the hard lighting effects that they use
for dramatic effect in black-and-white photography, owing to the loss
of color caused at the high spots. But an experiment will show that
in the case of oblique lighting, if the angle of the spotlights be less
pronounced (that is, the spot illumination be more from the front
than the side than in the case for black-and-white) , full color fidelity
can be maintained and the artistic effect still obtained by color con-
trast.

The producer will argue that if his main effects are achieved, a few
local losses of color saturation are of no consequence, and in any case
will not be appreciated by the audience. To a great extent that is
correct; but after examining Dufaycolor films on projection over a
number of years, the superiority of the results attained with definitely
flatter lighting than is used in black-and-white photography can be
vouched for; and, provided that the luminosity range lies (in the
case of the reseau now in use) within about 12.5:1, the range indicated
by visual examination of spectrograms, the results are of optimal
overall color fidelity.

EFFECT OF UNEVEN SLIT ILLUMINATION UPON

DISTORTION IN SEVERAL TYPES OF

VARIABLE-WIDTH RECORDS*

C. N. BATSEL AND C. H. CARTWRIGHT**

Summary. — The effect of uneven slit illumination upon the reproduction of vari-
able-width sound-tracks of the unilateral and bilateral types are analyzed. The
ground-noise reduction for unilateral tracks is considered, as accomplished by a
single-vane shutter so that the modulations are recorded symmetrically with respect
to the center of the track. For bilateral tracks both electrical biasing and double-vane
shutters are considered for effecting ground-noise reduction.

When the slit illumination increases linearly across the sound-track, bilateral
records either with electrical or shutter ground-noise reduction are not distorted.
When the illumination changes by 20 per cent across the sound-track by any uniform
function that would correspond to any actual case of faulty adjustment, the harmonic
distortion in no case exceeds 3 per cent for fully modulated signals. Further, the per-
centage of distortion decreases with the signal strength. Thus, while the reproduction
of variable-width recordings is subject to distortion by uneven slit illumination, it is
not excessive on equipment properly serviced.

In reproducing sound from either variable-density or variable-
width records, faulty illumination of the sound-track can cause vol-
ume attenuation and quality distortion. The nature of the distor-
tion depends upon the nature of the faulty illumination, but the
effect of uneven illumination of the reproducing slit is of special in-
terest. This is because variable-density records are not distorted,
and the distortion of variable-width records is a function of the il-
lumination and the type of variable-width track being reproduced.

This paper considers the effect upon the quality of sound repro-
duced from unilateral tracks with the anti-ground-noise (A. G. N.)
accomplished by a single-vane shutter, bilateral tracks with electri-
cal bias A. G. N., and bilateral tracks with double- vane shutter A. G. N.,
all as a function of the non-uniformity of illumination of the repro-
ducing slit. A harmonic analysis is given for three distinct types of
non-uniform illumination, and by combining these three types it is
possible to approximate most conditions met in actual reproduction.

* Received June 25, 1937.
** RCA Manufacturing Co., Hollywood, Calif.

476

UNEVEN SLIT ILLUMINATION

477

IZ'I

JU-hi>

i.l.*-b-+ ISL

i L** z T h
••!

Tract.

Rq>ax/ucer3/itl//tjmirtafon.

i Energy fellmy on Photocell

f//yM/llumir><rf/i/nKt:. TJi/s /J

/0%
"t-.^T^t ^ of Ia+>

FIG. 1. Unilateral track with shutter.

Z0%

FIG . 2 . B ilateral track with electrical bias .

jz 3- +cj/'rnut.

Trad:

Repnx/iKerS/iffl/um/noliori

O 10 ZO 30 4O SO 6O 70 6O 9O

FIG. 3. Bilateral track with shutter.

478 C. N. BATSEL AND C. H. CARTWRIGHT [J. S. M. P. E.

CALCULATION AND EXPLANATION OF DATA

In Figs. 1 to 9 the transmitting areas of three types of sound-tracks
are represented by the shaded portions. The signal is of constant
frequency u/2ir and the amplitude C is arbitrary and can vary from
C = 0 to C = h/2 for a unilateral track and C = h/4 for bilateral
tracks, h is the maximum width of the sound-track. The clearance
d, for A. G. N. R., is illustrated for each type of track, d is treated as
a variable, but only in the case of electrical bias does it influence
quality more than to change the amount of ground-noise. The
width of the light-beam illuminating the track is k, and we shall
consider only the case in which the slit width is sufficiently small as
not to introduce harmonic distortion.

In Figs. 1 to 10 are illustrated the intensity / of three types of slit
illumination across the total sound-track. The equation of the edge
of the sound-track and the equation of the intensity of the illumina-
tion are shown in each figure. It will be noted that for each figure
the track and slit illumination are represented by the same coordi-
nate system, but the coordinates are not the same for all the figures.
This is done to facilitate the mathematical calculations.

The radiant energy F transmitted by the film is indicated by an
integral of the form

E = f I k dy (1)

where / is the intensity of illumination of the film at any ordinate
y; k is the constant width of the reproducing light-beam; and dy is
the distance from y to y + dy. The limits of the integral are set by
the boundaries of the sound-track. The symmetry of bilateral
tracks makes it necessary to integrate only over one track. In Figs.
5, 6, 8, and 9 the distortion of both tracks obviously add. In Figs.
2 and 3 the integration has not been carried out because symmetry
considerations make it obvious that the distortion of one track will be
completely counteracted by the other.

Only modulated energy, E^, is reproduced from the photocell,
and therefore in substituting the integration limits the constant
terms due to track clearance have been omitted. It will be noted
that the results expressed as Emod represent a complete Fourier analysis
of the modulated signal reproduced. Naturally the result will be
exactly the same if, instead of regarding- the slit- width as con-
stant and the illumination as non-uniform, as we have done, the

UNEVEN SLIT ILLUMINATION

479

Only V* Harmonic. Distortion

PkKCtNTMC Ib of L>*Ib

FIG. 4. Unilateral track with shutter.

Ihedtoninceij'ifltrnduces a second harmonic, bulpnxtica/lyifcanbtneyleiied so :

I a

!z%

2/»

£

£

OnKj Z*& k It Harmonics

<! is r..,1. *' I

PBBCEMT«k&t Ib of I« + Ib

FIG. 5. Bilateral track with electrical bias.

480

C. N. BATSEL AND C. H. CARTWRIGHT rj. S. M P E.

Reproducer 3/tf ' I//t/m /nation

1-

Onlvj 2"-^ A. 3«* Harmonics

FIG. 6. Bilateral track with shutter.

K-M

PTA4+4M
y

FIG. 7. Unilateral track with shutter.

Nov., 1937] UNEVEN SLIT ILLUMINATION 481

illumination over the slit can be regarded as constant and the width
of the slit as changing according to the equation for / given each figure.
Relative to this last concept, it might be well to emphasize that we
have implied throughout that the slit-width was always sufficiently
small as not to introduce any harmonic distortion.

In Figs. 1 to 9 are shown graphically the percentage harmonic dis-
tortion for fully modulated signals as a function of the non-uniformity
of the recording slit illumination. It will be noted from the equa-
tions for Emod that the harmonic distortion decreases for small modu-
lations. For parabolic non-uniformity the distortion is approxi-
mately proportional to the square of the amplitude of the signal.
This has been illustrated graphically in the figures by showing the
distortion for 50 per cent modulation. Thus the graphs represent
the distortion introduced by faulty slit illumination in the most un-
favorable light.

In addition to varying the non-uniformity of slit illumination ac-
cording to the three general types shown in Figs. 1 to 9, the distortion
of other types can be computed by considering the addition of two
types as is illustrated in Fig. 10. In computing the distortion due to
two of the general types it is necessary to add the distortions alge-
braically, for usually the distortions compensate one another.

RESULTS

(1} Slit illumination in a reproducer that increases perfectly uni-
formly across the slit produces 2nd-harmonic distortions in a unilat-
eral track. The percentage of distortion is almost proportional to the
signal strength and the variation in intensity across the slit.

(2} Bilateral tracks with electrical bias or shutter bias are not in-
fluenced by a perfectly uniform change in illumination over the en-
tire sound-track.

(3) With non-uniform slit illumination that is either greatest or
least at the center, unilateral tracks produce only 3rd harmonics.
For the same illumination, bilateral tracks produce a 2nd harmonic
and a slight 3rd harmonic.

(4) The more unsymmetrical the non-uniformity of illumination
about the middle of the slit, the more bilateral tracks are favored
°ver a unilateral track. This is illustrated by Fig. 10.

(5) The amount of distortion produced by any type of non-uni-
formity of illumination is almost directly proportional to the amount
of non-uniformity.

482

C. N. BATSEL AND C. H. CARTWRIGHT [J. S. M. P. E.

7.£+#^

-y

FIG. 8. Bilateral track with electrical bias.

of la •«• Ib .

FIG. 9. Bilateral track with shutter.

Nov., 1937]

UNEVEN SLIT ILLUMINATION
CONCLUSION '

483

The effects of three distinct types of non-uniform slit illumination
upon the reproduction of three types of variable-width sound-track
are treated by harmonic analysis. The nature and amount of dis-
tortion produced are functions of the type and amount of non-uni-
form slit illumination, the type of sound-track, and the signal strength.

r

FIG. 10. Method of computing distortion for
tracks other than those shown in Figs. 1 to 9.

Although non-uniform slit illumination in general distorts the repro-
duction of variable-width sound-track, the amount of distortion
is usually less than 1 per cent; thus, by properly servicing a repro-
ducer, the amount of distortion due to non-uniform slit illumination
can be made negligible for reproducing all types of variable-width
sound records.

THE ORGANIZATION AND ACTIVITIES

OF THE

RESEARCH COUNCIL OF THE ACADEMY OF MOTION
PICTURE ARTS AND SCIENCES*

WILLIAM KOENIG**

Summary. — The details of the organization of the Research Council of the
Academy of Motion Picture Arts and Sciences are outlined, and brief sketches are
presented of the work of several of the more important Committees working under the
auspices of the Council, including the Committee on Improvement of Release Print
Quality, the Silent Camera Committee, Committee on Screen Illumination, Com-
mittee on Industrial Education, the Scientific Committee, and the Sound Recording
Committee.

Although many industries have supported organizations devoted to
cooperative research and development, each of which has been molded
to fit the particular requirements and demands of that particular in-
dustry, we of the motion picture producing industry in Hollywood
believe that in the Research Council of the Academy of Motion Pic-
ture Arts and Sciences we have an organization that is both unique
and unusual.

Many of you are probably more familiar with the organizations in
other industries than I am, such as the American Petroleum Institute,
the National Electric Light Association, the National Automobile
Chamber of Commerce and many others, all of which conduct tech-
nical organizations of one sort or another as part of their activities.

Although the Academy of Motion Picture Arts and Sciences has
engaged in some cooperative research ever since its organization in
1927, the Research Council as it now functions was organized in 1934,
and its first chairman after the reorganization was S. J. Briskin, Ex-
ecutive Vice-President of RKO-Radio Studios. The operation of the
Research Council is patterned after the technical organizations of the
various trade associations, as their methods could be applied to the

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
21, 1937.

** Chairman, Research Council, Academy of Motion Picture Arts and Sciences;
General Manager, Metro-Goldwyn-Mayer Studio, Culver City, California.
484

ACADEMY RESEARCH COUNCIL 485

motion picture industry, for the sole purpose of giving to the produc-
ing companies here in Hollywood, and their affiliates throughout the
world, the benefit of the fullest cooperation of all the technicians en-
gaged in the production and exhibition of motion pictures, to eliminate,
wherever possible, duplication of effort and expense.

As an organization of technical men you are most interested in the
details of the work of our many Committees. The Council is com-
posed of one representative from each of the producing companies
participating in the program, and acts as a Board of Governors ad-
vising on and directing the work of the Committees.

In 1934 the Research Council had eight cooperative projects in the
hands of eight separate committees enlisting the interest of approxi-
mately seventy-one technicians. Its activities have grown until at
the present time it has thirty-six committees with approximately one
hundred and eighty different company representatives working on
these committees. During the past year we had more than two hun-
dred and fifty committee meetings, averaging approximately five a
week.

To acquaint you with all the details of our work would take days,
but I will attempt to give you in the next few moments a brief sketch
of the work of several of our Committees. Of major importance at
the moment is the Committee on Standardization of Theater Sound
Projection Equipment Characteristics, which, under the Chairman-
ship of John Hilliard of Metro-Goldwyn-Mayer Studios, has recently
recommended a Standard Electrical Characteristic that should
greatly improve the quality of sound in all theaters.

A Committee on Improvement of Release Print Quality, under the
Chairmanship of L. E. Clark of the Dunning Process Company, has
for many months past been investigating every possible method that
might be adapted to an eventual standard density. As we all know,
there is very little actual coordination among the few laboratories
here in Hollywood processing negative film and the many laboratories
throughout the world making release prints. The last report of this
Committee indicates that it has finally solved the problem, and within
the next few months the industry will have a simple and effective
method of comparing print densities to a standard calibrated density-
measuring device that we "plan to build and install here in Hollywood
as a service to the entire industry.

The Silent Camera Committee, under the Chairmanship of Virgil
Miller, has been at the service of the camera manufacturers and the

486 W. KOENIG LT. S. M. P. E.

producers for the purpose of testing newly developed, so-called silent
cameras, and for assisting in the development and testing of various
blimp- and camera-silencing devices. In connection with its work
the Committee has recently drawn up a set of camera noise testing
conditions which we plan to make available to the industry so that
the results of camera tests according to this standard procedure and
under these standard conditions anywhere in the world will compare
directly with the results of tests made here in Hollywood.

The Screen Illumination Committee, under the Chairmanship of
John Aalberg of RKO-Radio Studios, although originally set up to
consider illumination conditions in studio viewing rooms only, some
months ago expanded the field of its activities and is now working on
plans for a national survey to determine actual illumination condi-
tions in the theater field and to give the release printing laboratories
accurate and definite data as to the screen illumination in the theaters.

As a result of a number of complaints sent to us by the producing
companies regarding arc light noise, which has proved troublesome to
the studio recording departments, we have recently organized a Com-
mittee under the Chairmanship of Thomas Moulton of United Artists
Studios, to investigate the problem for the purpose of determining the
causes of the trouble and suggesting remedies for it.

In addition to these purely technical projects dealing with motion
picture production and exhibition to which we have previously con-
fined ourselves, we have this last year ventured into an entirely new
field — i. e., that of industrial education. As a first step in this ac-
tivity, the Committee on Industrial Education arranged a prelimi-
nary course in sound recording with A.P. Hill of Electrical Research
Products, Inc., as instructor.

The first course, given in the Spring of 1936, met with such tre-
mendous success in the studios that upon the unanimous request of
the studio sound department heads and a large number of techni-
cians whom we could not accommodate in that course, we repeated
it again this fall.

In addition to this preliminary course, a more comprehensive ad-
vanced course dealing with theory and operation of sound equip-
ment was given this fall, meeting twice a week for twenty-four weeks
at the Hollywood High School.

The services of the four instructors who handled this advanced
course were made available to the Council through the cooperation
of their employing companies. The instructors, all of whom have

Nov., 1937] ACADEMY RESEARCH COUNCIL 487

given a great deal of time and effort to putting the course over are
L. E. Clark, John Milliard, Fred Albin of United Artists Studios,
and Harry Kimball of Metro-Goldwyn-Mayer.

We have trained in the courses a total of two hundred and thirty-
five studio sound department employees, all of whom will be of much
greater value to their employing companies this year than they were
last because of having undertaken the study. In setting up these
courses it was specified that enrollment would be limited strictly to
employees of the studios who are already engaged in sound record-
ing, inasmuch as it was not our purpose to complicate the employ-
ment situation by teaching men who were not already engaged in
this work.

The field of internal industrial education is, of course, unlimited,
and there are a great variety of subjects that might be discussed by
groups within the studios to the ultimate great advantage of their
companies, and we contemplate expanding this part of our work as
rapidly as our facilities and finances will permit.

The Committee on Industrial Education, under the Chairmanship
of Dr. J. G. Frayne of Electrical Research Products, Inc., assisted
by Barton Kreuzer of the RCA Manufacturing Co, Dr. Burton F.
Miller of Warner Brothers Studio, William Thayer of Paramount
Studio, and Ralph Townsend of 20th Century-Fox Studio, is now
discussing additional plans for a very general course in sound record-
ing for film editors, a course in the latest developments of acoustics
for sound technicians, several laboratory subjects, new developments
in electrical testing, new developments in the re-recording and re-
production of music and other subjects.

In the Scientific Committee, under the Chairmanship of Carl
Dreher, the producing companies have available a group of highly
trained technicians who as a body are keeping themselves fully
informed, from the standpoint of the producing studios, of every
development in television. The producers look upon this Committee
as a highly qualified group of "watch dogs" who are following tele-
vision s every move.

Our Sound Recording Committee, under the Chairmanship of
E. H. Hansen of 20th Century-Fox Studio, consisting of the heads
of the major sound departments, is concerned with group improve-
ments in studio recording practices. At the present time this Com-
mittee is conducting five or six separate projects, one of which is
of particular interest to me as a producer. As you all know, sound

488 W. KOENIG

as heard in the theater is quite different from the original sound re-
corded upon the set. The addition of sound effects, background
music, off-stage dialog, etc., sometimes completely changes the com-
plexion of a scene.

Recognizing the importance of the dubbing operation to a fin-
ished picture, the Sound Recording Committee recently decided to
conduct an interesting experiment. The dialog, background music,
and sound effects tracks of one reel of a completed production are
now being sent through the dubbing operation in each of our eight
studios. When finished, we shall have eight different versions of
the same reel, all dubbed from the same original tracks — and I ven-
ture to say that eight very different finished versions will come out
of this experiment.

I hope that the Sound Directors will not confine this reel to them-
selves but will show it to every sound technician in all the studios,
in order that each will get the benefit of the comparison between the
work of the other studios' dubbing departments.

In closing I might say that the Research Council is steadily build-
ing up a background of achievement that has not as yet been marred
by a single failure.

A LINEAR DECIBEL-SCALE VOLUME INDICATOR*
F. G. ALBIN**

Summary. — A new design of volume indicator for use in sound recording is de-
scribed, embracing the features of peak amplitude response and a linear decibel scale.
The peak response characteristic results in a better indication of peak amplitudes,
and thereby affords protection of the modulator against overloads. The linear decibel
scale extends the useful range of the indicator about 12 db. , thereby indicating low levels
formerly imperceptible.

The volume indicator is the chief tool of the sound recording mixer
in gauging his recording level, which must be maintained consistently
within limits for several reasons. First, the range must be com-
pressed so that a satisfactory signal-to-noise ratio is always main-
tained, even at the lowest recording level. Furthermore, since
there is a definite limit to the amplitude that can be accommodated
by the modulator, the level must never be so high as to allow the peak
amplitudes to overload the modulator.

The nature of recorded sound is wide and varied. The wave-forms
are most frequently very complex, with peak factors often in excess
of 15. Furthermore, the waves are transient, and may persist only
for relatively short periods. For safeguarding the modulator against
overloads, and since the modulator follows the wave-form, the vol-
ume indicator should respond to the peak amplitudes, and the period
of response should be shorter than the period of duration of the tran-
sient wave. Fortunately, however, there is a lag in the response of
both the ear and the eye, and overmodulation may be permitted for
short intervals without serious degradation of fidelity if the interval
is so short as not to be observed on the indicator. Therefore, the re-
quired speed of response of the volume indicator is somewhat reduced.

Because of the transient nature of the recorded sound, the indicat-
ing meter should be highly damped, so as not to overshoot the ulti-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
18, 1937.

** United Artists Studio Corp., Hollywood, Calif.

489

490

F. G. ALBIN

[J. S. M. P. E.

mate reading. A slow return from the indicated reading is allowable
and, in fact, preferred, since it allows the mixer time in which to reg-
ister the indication.

70%

FIG. 1. (.4) Linear amplitude scale; (B) linear decibel scale.

Level Range. — The uncompressed range of sound level en-
countered in recording covers approximately 80 db. Modern record-
ing latitude does not exceed 50 and, in general, is limited to about 30
db. The usual volume indicator has a range of 12 db. for the upper
85 per cent of its scale. Allowing the upper 6 db. of the scale for
exceptionally high levels establishes the maximum normal level, or
100 per cent modulation, at midscale. The first 15 per cent deflec-
tion will be disregarded because of the considerable non-linearity in
that region and the inaccuracy of readings. The 15 per cent low limit
will be arbitrarily chosen to apply to both types of meters while com-
paring them.

FIG. 2. Circuit of linear-decibel volume indicator.

The remainder of the 85 per cent or 30 per cent of the scale is left
for the 6-db. useful range of the meter. Any level lower than 6 db.
below overload, or less than 50 per cent modulation, causes less than
15 per cent scale deflection, leaving only 6 db. as the useful range of
the meter. For that reason, background sounds, such as music, or

Nov., 1937]

DECIBEL-SCALE VOLUME INDICATOR

491

low-level speech, such as whispers, are practically imperceptible on
the indicator, and the monitor must be relied upon for judging the
level. The recent extension of the recording range aggravates the
condition, and the volume indicator is wholly inadequate to indicate
levels over the range recorded. In practice, full-scale deflection is
often used for 100 per cent modulation, thereby sacrificing the indi-
cations above the overload point and extending the useful range by
approximately 6 db.

Linear Decibel Scale. — A linear decibel scale is shown in
Fig. 1. Here, as with the former scale, the full deflection is 6 db.
above 100 per cent modulation, or 200 per cent. However, 100 per
cent modulation occurs approximately at 85 per cent of full scale,
leaving about 70 per cent of the scale for the useful range. Fur-
thermore, 15 per cent of the scale
represents 18 db. below 100 per
cent modulation. The useful
range is 18 db., which is 12 db.
greater, or 4 times the amplitude
of the former. Also, 70 per cent
of the scale is useful, as compared
with 30 per cent of the former.

The ear recognizes equal
changes of level as equal incre-
ments of sensation; in other
words, it has a logarithmic re-
sponse to change of level. The
volume indicator should respond

likewise; equal increments of sound level should cause equal incre-
ments of volume indicator deflection. Therefore, the deflection of
the volume indicator should be proportional to the input level in
decibels.

Fig. 2 is the circuit diagram of the linear decibel peak reading vol-
ume indicator, employing a standard volume indicator meter. Es-
sentially, the circuit consists of a stage of amplification, a full-wave
vacuum tube rectifier, and a d-c. amplifier having an exponential re-
sponse to input. The first amplifier has a main gain control calibrated
in decibels and a vernier control for compensating for tube amplifica-
tion variations. Other vernier adjustments, not shown, correct for
other tube variations, and certain other refinements are omitted

FIG. 3. Linear decibel scale.

492 F. G. ALBIN

from the drawing. The diode rectifier may be enclosed in the en-
velope with the amplifier.

The d-c. amplifier employs a tube having three grids. The first
grid is connected to the plate through a resistance. The second grid
is used as a space-charge grid, and the third as the control grid. A
bridge circuit in the anode circuits is so adjusted that the normal
meter current is zero. The input signal applies a negative potential
to the control electrode and lowers the plate current. According
to the behavior of the usual multiple-electrode tube, the current in
the second grid increases with decrease of plate current. Both these
changes contribute to unbalancing the bridge and causing current
to flow through the meter.

It is beyond the scope of this paper to describe in detail the action
that causes the exponential response. Briefly, however, it is due to
connecting the first grid to the plate. As the plate current decreases,
the potential increases, and thus the first grid voltage and the current
both increase. The combined plate and first grid current decrease,
however, and in a manner that is proportional to the logarithm of the
control grid voltage change over a limited range.

Excessive input voltage merely reduces the plate current to zero,
beyond which there is no further change of tube or meter currents, and
no damage to the tube or meter is possible. The meter is standard
in every respect except for the linear decibel scale (Fig. 3). The
bridge circuit, which balances out the zero signal anode currents, has
the additional merit also of restoring the meter current to zero in the
event that the cathode current of the tube is stopped. A further
feature is that variations of B voltage are balanced out of the meter
circuit to a large degree.

A choice of tubes is necessary for best performance. With se-
lected tubes, the response is linear for at least 24 db. Establishing
0.5 db. as the tolerance over the 24-db. range, the proportion of good
to rejected tubes obtained on the open market was one to three.
Extensive tests of the apparatus have proved it to be practicable and
popular as a volume indicator for recording.

DISTORTION IN THE REPRODUCTION
OF HILL-AND-DALE RECORDING*

M. J. DI TORO**

Summary. — In the reproduction of a hill-and-dale recording, the curve traced by
the reproducer stylus differs from the recorded curve, with (he consequent introduction of
both frequency and amplitude distortion. This distortion is here catted "tracing dis-
tortion," and must be tolerated only in virtue of the physical necessity of a finite tip
radius for the reproducer stylus. A description is given of the results obtained in a
study of this phenomenon, together with curves and formulas for the quantitative deter-
mination of the magnitude of both the amplitude distortion (i. e., harmonic generation)
and the frequency distortion (i. e., decay in fundamental), as functions of the amplitude
and frequency of the recorded undulation, the linear groove speed, and the tip radius
of the reproducer stylus.

A mong other conclusions reached, it is shown that the maintenance of the minimum
radius of curvature of the recorded undulations at least equal to or larger than the tip
radius of the reproducer stylus is an extremely inaccurate criterion of good-quality
reproduction. For "constant-velocity" recordings, less than 10 per cent rms. har-
monic generation is obtained when the minimum radius of curvature of the recorded
undulation is greater than 5 times the tip radius of the reproducer stylus. Moreover,
the generation of harmonics due to tracing distortion is a much more serious limitation
upon the quality of the reproduction than is the loss or attenuation of fundamental
frequency, as, for example, in cases where the loss of fundamental is only 2 db., the
harmonic generation is prohibitively high, being much greater than 10 per cent.

The Introduction and Section I give a physical account of the phenomenon of trac-
ing distortion and deal with all the data necessary for a practical application of the
formulas derived in Section II.

INTRODUCTION

An electrical phonograph system consists essentially of a record-
driving mechanism, a reproducer, an amplifier, and a loud speaker.
Each of these component devices of the system is capable of produc-
ing distortion of some kind, which will render the reproduced sounds
an improper mechanical-acoustical conversion of the undulations re-
corded on the record. Most of this distortion may be classified as
being one or both of two general types. One type is known as fre-

* Presented at the Fall, 1937, Meeting at New York, N. Y.; received Sept. 1.
1937.

** Thomas A. Edison, Inc., West Orange, N. J.

493

494 M. J. Di TORO [J. S. M. P. E.

quency distortion, and arises from attenuation or magnification of
certain portions of the frequency spectrum passing through the phono-
graph system. The other type is known as amplitude distortion, in
which the magnitude of the reproduced sound is not proportional to
the magnitude of the recorded undulation. From an analysis of am-
plitude distortion, it is known1 that when the wave-shape of the re-
corded undulation is sinusoidal, the distorted reproduced sound con-
sists of a fundamental component of the same frequency as the re-
corded undulation, plus harmonic components that do not exist in the
recorded undulation.

Inasmuch as amplifiers and loud speakers are used to a considerable
extent in many forms of sound systems, their characteristics with re-
spect to distortion have been studied in great detail, so that it is now
possible to design devices of this type in which the distortion is at
such a low level as to be negligible. Distortion arising from speed
variation (flutter) in the record-driving mechanism has been mate-
rially reduced by ingenious designs of speed-governing systems.2'3 A
considerable amount of study has also been given to phonograph
reproducers4'5 to eliminate both frequency and amplitude distortion.
In well designed reproducers the mechanical transducing system can
usually be made such that both these forms of distortion are again
negligible.

A remaining form of distortion in the phonograph system is, how-
ever, present in the phonograph reproducer. This distortion does
not arise in the mechanical system of the reproducer itself, but occurs
because of the finite radius of the reproducer stylus that is required
to avoid excessive wearing of the record. When the tip dimension of
the reproducer stylus becomes comparable with the wavelength of
the undulations in a phonograph record, the stylus will not follow a
path of exactly the same wave-shape as that followed by the sharp
cutting stylus of the recorder used in making the record. An extreme
case occurs when the radius of curvature of the recorded undulation
becomes smaller than the tip radius (of curvature) of the reproducer
stylus. For this condition, it is quite obvious that the reproducer
stylus can not follow precisely the recorded undulation. In the past
literature on this subject many authors6'7 have regarded this to be a
limiting condition for phonographic reproduction, and have attempted
to design the system so that the minimum radius of curvature of the
recorded undulation would always remain at least as large as the radius
of curvature of the reproducer stylus. However, even when this

Nov., 1937]

DISTORTION IN REPRODUCTION

495

condition is met, those who are familiar with phonograph practice
recognize certain deficiencies in the reproduction of phonograph rec-
ords. For instance, on long-playing disk records in which the outer
groove has several times the length and therefore several times the
linear velocity of the inner groove, a loss at high frequencies and a
raucous quality have been noted in the reproduction from the inner
grooves. It has been noted that this change is less marked when the
amplitude of the recorded undulation is reduced. Some engineers,

FIG. 1. Tracing distortion: (1) recorded un-
dulation; (2) parallel curve to curve 1; (3) path
of reproducer stylus.

ill order to avoid this apparent loss at the higher frequencies, have re-
sorted to arrangements that modify the frequency characteristic of
the recording system so as to increase the high-frequency response of
the system at the inner grooves.

Since no quantitative data appear to be available on this type of
distortion, a detailed study of it in hill-and-dale recordings has been
undertaken with the view of establishing such quantitative data.
This type of distortion will be called "tracing distortion," since its
occurrence is directly connected with the inability of the finite re-
producing stylus to trace faithfully the undulations of a phonograph
record. Section / of this paper will be devoted to a physical consid-

496 M. J. Di TORO [J. S. M. P. E.

eration of the phenomena, and a summary of the practical design
criteria established during the course of the study. The mathemati-
cal derivation of the formulas used in Section I is given in Section II.

Fig. 1 is an enlarged cross-sectional view of a hill-and-dale phono-
graph record, showing a reproducer stylus in three positions as the
record passes under it. The amplitudes of the undulations in the
record are exaggerated in the interest of a clearer demonstration of
the effects being discussed. The surface of the recorded undulation
(1) should, if a properly designed recorder is used in making the rec-
ord, be the desired recorded version of the signal input that actuated
the recorder. Curve 2 is a dotted line drawn parallel to curve 1 so
that every point on 2 is higher, in a direction along the vertical stylus
axis, than a corresponding point of 1 by an amount equal to the radius
of the reproducer stylus. If this stylus is to trace the recording faith-
fully without giving rise to tracing distortion, its center should follow
curve 2. However, because of the varying point of contact between
the reproducer stylus and the record, the center of this stylus ball
does not follow curve 2, but follows another curve, 3, which deviates
appreciably from curve 2. It is noted that the undulation of the
record shown at the center of Fig. 1 has a radius of curvature less than
that of the reproducer stylus, so that the latter actually bridges the
undulation without touching the bottom of it. Very serious dis-
tortion, therefore, occurs at this point. However, it is also noted
that at other points along the recorded undulation where this condi-
tion does not apply, the distortion is still quite appreciable.

Now, it is obvious that a number of factors determine the extent
of this tracing distortion. As the reproducer stylus radius is made
smaller and smaller, it is clear that the path followed by the stylus
more nearly approaches the wave-form of the recorded undulation.
Furthermore, when the linear speed of the record during recording is
increased so that the wavelengths of the undulations are increased
without increasing their amplitudes, tracing distortion is also de-
creased. It is also obvious that when the amplitude of the recorded
undulations is decreased, without changing any of the other conditions,
the distortion is lessened. Moreover, the frequency of the recorded
undulations is also a determining factor : the higher the frequency the
closer the undulations, and therefore the greater the distortion. It
is therefore seen that tracing distortion, which arises from the dis-

Nov., 1937]

DISTORTION IN REPRODUCTION

497

similarity between the curve traced by the reproducer stylus and the
recorded undulations, is a function of four parameters of the system,
these being (I) the tip radius of the reproducer stylus, (2) the linear
groove speed, and (3) the amplitude and (4} frequency of the recorded
undulation.

A quantitative measure of this tracing distortion is contained in an
analysis of the frequency and amplitude distortion components of
the curve traced by the reproducer stylus when reproducing a re-
corded undulation of sinusoidal wave-shape. The results of such an
analysis are given graphically by Fig. 2, which shows the decay in

100
90

80
I 70

I

; so

40

FUNDAMENTAL

RMS 2ND 3RD 4TH HARMONIC-

2ND HARMONIC

3RD HARMONIC
4TH HARMONIC

VALUES OF P « 2RF/V / I +/ V \2
' V \6AFJ

FIG. 2. Components of traced curve: decay of fundamental, and ratios
of spurious harmonic amplitudes to amplitude of fundamental in traced

amplitude of the fundamental component of the traced curve rela-
tive to the recorded undulation and the ratios of the spurious har-
monic amplitudes to the amplitude of the fundamental in the traced
curve. .It is seen that these curves are universal, in the sense that
they are functions of a single dimensionless parameter P. This pa-
rameter will be called "tracing factor," and is related to the four sys-
tem parameters mentioned above by the expression

2RF

n

P, the tracing factor (a pure number having no dimension).

R, the tip radius of the reproducer stylus in inches.

V, the linear groove speed of the record in inches per second.

498

M. J. Di TORO

[J S. M. P. E.

A, the amplitude of the recorded undulation in inches.

F, the frequency of the recorded wave in cycles per second.

For most cases, formula 1 for determining the tracing factor P may be
simplified into an approximate form. This approximation is valid
when (V/6AF)Z is much greater than unity so that, when this is true,
P becomes equal to

p-1-^ w

This distortion of the curve followed by the reproducer stylus is
transmitted through the reproducer transducing system, and results

„. 30

FUNDAMENTAL

RMS 2ND 3RD 4TH HARMONIC

2ND HARMONIC-

* i

z
111

4 Z

o

e i

u.

8 *

10 O

15 01

o
20

30

.7 1.0

VALUES OF P» g RF/V/lW V \2
' V ^6AF/

FIG. 3. Output components of velocity responsive reproducer: decay
of fundamental, and ratios of spurious harmonic amplitudes to amplitude of
fundamental in reproducer output.

in an output signal of the reproducer that is also distorted, even, of
course, when no undesirable distortion is present in the transducing
system.

Now, the vast majority of phonograph reproducers are intended to
be used in the reproduction of so-called "constant- velocity" records.
These records are made in a recording system in which recorded un-
dulations are obtained whose product of amplitude and frequency is
constant when the supposedly properly designed recorder used in
making the recording is fed at a constant input level over the major
range of frequency of the transmitted band. In the reproduction of
such a recording, it is clear that a reproducer is to be used whose out-

Nov., 1937]

DISTORTION IN REPRODUCTION

499

put signal must be proportional not merely to the amplitude of mo-
tion of its stylus, but rather to the product of amplitude and frequency
of the stylus motion. A reproducer of this type is velocity-re-
sponsive, since in a sinusoidal motion of the stylus the maximum ve-
locity attained is proportional to the product of amplitude and fre-
quency of the stylus motion. In the reproduction of a recorded un-
dulation of increasing frequency but of fixed amplitude, the output
signal obtained with a velocity-responsive reproducer increases with
increase of frequency. This fact is made use of in deriving the curves
of Fig. 3 showing the decay of the fundamental and the ratios of the

OB DECAY OP
FUNDAMENTA

*

Q 2

<r Z
10 O

fj

1s

tr
^

^~.

TRACING DISTORTION IN
VELOCITY RESPONSIVE SYSTEM

s

k^

's.

\

s

MAXIMUM AMPLITUDE OF RECORDED
UNDULATION A- 002" AT 250 C.P.S.
REPRODUCER STYLUS RADIUS R=,002"
LINEAR GROOVE SPEED V> 15" SEC

^

/

/

•^

S

S

jS

^S'

^^.

*^*^

_^-

*•»—

••—•*

*—

•—

P-J

.16 .2

3 .4 .5

IX)

15 2.

3. 4. 5.

7.

10.

FREQUENCY IN KILOCYCLES PER SECOND

FIG. 4. Tracing distortion in typical velocity-responsive system: decay
of fundamental and ratio of rms. amplitude of 2nd, 3rd, and 4th harmonic
to amplitude of fundamental.

spurious harmonic amplitudes to the amplitude of the fundamental
in the output of a velocity-responsive reproducer, of substantially
flat frequency characteristic, whose stylus is following a sinusoidal
recorded undulation and thus has a motion composed of a funda-
mental and spurious harmonic components as shown in Fig. 2. The
universal nature of the curves of Fig. 3, obtained through the intro-
duction of the tracing factor P, is desirable since all the data neces-
sary for determining the tracing distortion arising from any com-
bination of values of the four system parameters A , F, R, and V are
available in concise form. As an example, the curves of Fig. 4 are
obtained directly from Fig. 3, and show the response loss of funda-
mental and the rms. 2nd, 3rd, and 4th harmonic generation in a "con-
stant-velocity" system in which the maximum amplitude of the re-

500

M. J. Di TORO

[J. S. M. P. E.

cording is A = 0.002 inch at 250 cps. and decreasing thereafter with in-
creasing frequency, the reproducer stylus tip radius R = 0.002 inch,
and the linear groove speed V = 15 inches per second.

Fig. 5 shows the results of some experimental measurements of the
amplitude distortion component of tracing distortion in the repro-
duction of single-frequency recordings at 1500 cps. on wax records,
together with the theoretically expected values of distortion as ob-
tained from Fig. 3. A piezoelectric velocity-responsive reproducer hav-
ing a tip stylus radius of 0.010 inch was used in these tests. The 2nd

50
45
40
35

25
20

15
10
5

LINEAR GROOVE SPEED V- 6.3 IN./SEC.

V- II IN/SEC.

V« 17 IN./SEC.

.005 .007 .010 .015 .02 .03 .04 .05 .07 .1 .15 .2

AMPLITUDE OF RECORDED WAVE
IN THOUSANDTHS OF AN INCH.

FIG. 5. Comparison of experimental and theoretical
results for F = 1500 cps. and R = 0.010 inch. The full-line
curves are obtained from Fig. 3; the dots show the experi-
mental results.

harmonic distortion component in the reproducer output was isolated
by a suitable electrical band-pass filter. Correction factors were
introduced to account for the response characteristic of the repro-
ducer and its associated amplifier, and for the insertion loss of the
band-pass filter. It is seen that the values of the four system pa-
rameters A, F, R, and Fin these tests were varied so as also to present
conditions in which the minimum radius of curvature of the recorded
sinusoidal undulation was less than that of the reproducer stylus.
Inasmuch as the conditions of the tests were always such that R/A ,
the ratio of the reproducer stylus radius to the amplitude of the re-
corded undulations, was never less than 100, some comments are

Nov., 19371 DISTORTION IN REPRODUCTION 501

appropriate in considering the applicability of the theoretical data of
Fig. 3 to other values of the system parameters and to other record
materials. In deriving the curves shown in Figs. 2 and 3, it is assumed
that the record is infinitely stiff so that the reproducer stylus follows
a curve parallel to the curve traced by the center of a circle rolling up
and down the recorded undulations and having a radius equal to that
of the reproducer stylus. Now, the force exerted upon a record by
the reproducer stylus creates very great pressure intensities in the
record material so that the latter must yield to some extent. How-
ever, reproducers must be and are designed so that in a single playing
of a phonograph record only a very small amount of record wear takes
place. Since record wear is essentially a disfigurement of the record
and appears to be a function only of the relative force between the
reproducer stylus and the record, it is plausible to conclude that dur-
ing any one playing of a phonograph record the large pressure inten-
sities to which the record is subjected are not sufficient to deflect the
record beyond the elastic limit of the record material. It thus follows
that the record deflection is very nearly proportional to the force
exerted by the reproducer stylus. Record deflection will thus not
introduce appreciable amplitude distortion in the reproducer stylus
motion, but will introduce an increasing loss in the motion for the re-
production of higher and higher frequencies. This loss may, how-
ever, be compensated by frequency-discriminating circuits in either
the mechanical or electrical systems of the reproducer. The initial
assumption of a stiff record material thus appears to be justified, since
even when the record deflects, no appreciable amplitude distortion
appears, and the frequency distortion that does appear may suitably
be corrected. It is noted, however, that when a recorded undulation
is being reproduced whose radius of curvature is equal to or smaller
than the radius of the reproducer stylus, the bridging contact con-
dition of the stylus with the record, and the impulsive forces generated
by the velocity discontinuities demanded of the stylus motion, result
in the latter being somewhat different from that assumed theoreti-
cally. However, it is to be seen later that when this bridging condi-
tion of the stylus exists, an amount of amplitude distortion is pro-
duced that is far beyond that tolerated in high-fidelity systems. For
this reason, a more accurate analysis of the conditions prevailing at
and beyond the reproducer stylus bridging condition is of secondary
practical interest.

It is clear upon inspection that tracing distortion tends to increase

M. J. Di TORO [J. S. M. P. E.

with frequency, thus making more difficult distortionless reproduction
over a wide range of frequency. However, if the material that is to
be recorded is speech, the tracing distortion arising will be generally
less serious than for music. This is due to the fact that for frequen-
cies higher than 200 cps. the sound pressure amplitudes of speech
vary approximately inversely with frequency.8 Now, since in a ve-
locity-responsive system an input into the recording system of fixed
level throughout the major portion of the frequency spectrum results
in recorded undulations whose amplitudes decrease inversely with in-
crease in frequency, it follows that for speech recordings the ampli-
tude of the recorded undulations decreases inversely with the square
of the frequency. This means that F*A is constant, and, for given
values of reproducer stylus radius and linear groove speed, formulas 1
and 2 show that P is substantially constant. A glance at Fig. 3 re-
veals that when P is constant the amount of distortion present is
fixed and thus does not increase with increase in frequency.

It is noted on inspection of Fig. 3 that the generation of harmonics
is a much more serious limitation upon the quality of reproduction
than is the loss or attenuation of fundamental frequency. For ex-
ample, in cases where the loss of fundamental is only about 2 db., the
harmonic distortion is prohibitively high, being much greater than
10 per cent. It is also noted that whenever systems are designed so
that the harmonic content is less than 10 per cent, the loss in funda-
mental is negligibly small. If, therefore, in a long-playing record there
is noticeable loss at high frequencies in the reproduction from the in-
ner grooves, this must invariably be accompanied by rather serious
harmonic distortion, and indicates that the tracing factor P of the
system must be reduced to a considerable extent by decreasing the
recording amplitude or reproducer stylus radius or by increasing the
linear groove speed if distortionless reproduction is to be approached.
Any attempt to increase the high-frequency response by increasing
the input and output characteristics of the recorder or reproducer in
this high-frequency range will result in more serious harmonic genera-
tion and thus in poorer overall quality.

It is believed that tracing distortion is responsible for much of the
distortion in the reproduction of phonograph records, particularly
the distortion that occurs during loud passages, which is frequently
ascribed to dirt on the record or failure of the reproducer to stay in
contact with the record groove. It is to be noted that maintenance
of minimum radius of curvature of the recorded undulations at least

Nov., 1937] DISTORTION IN REPRODUCTION 503

equal to or larger than the tip radius of the stylus is an extremely in-
accurate criterion of quality. Under this condition, the tracing
factor is approximately equal to 0.3, and at this point the curves of
Fig. 3 indicate the enormous value of 50 per cent rms. harmonic
generation. It is suggested that under no circumstance should the
total harmonic generation, which is shown in Section II to be a mea-
sure of the raucous characteristic of the reproduction, be permitted
to exceed 10 per cent. Thus if it is specified that a maximum rms.
harmonic content of 10 per cent may be tolerated, then the minimum
radius of curvature of the recorded undulations must be at least five
times the radius of the reproducer stylus for a velocity-responsive
reproducer. Using the simplified formula 2, less than 10 per cent
harmonic content is present when V2 is greater than 200 RAF2 for
velocity-responsive systems, where, as before, V is the linear groove
speed in inches per second, R is the radius of the reproducer stylus in
inches, F is the frequency of the recording in cps., and A is the ampli-
tude of the recorded undulation in inches. These simple design
formulas impose rather stringent specifications upon the system
parameters, but represent low-distortion conditions in line with the
modern trend toward higher-fidelity systems. Even more stringent
requirements are needed than those specified above if levels of har-
monic distortion lower than 10 per cent are expected.

The analysis given above is, of course, limited to hill-and-dale re-
cordings, but the same general method of attack may be used in other
systems involving tracing undulations of any sort with a device of
finite dimensions. For instance, a similar phenomenon is tracing a
photographic recording with an aperture of finite width. Previous
analyses in the literature9'10 indicate in this case that in tracing a
single-frequency recording the wave-shape remains unaltered, but
an increasing loss in fundamental occurs as the width of the slit ap-
proaches the wavelength of the recorded signal. In recording such
photographic records, however, both a loss of fundamental and a
generation of spurious harmonics occur.

For those who are interested, the following section contains a de-
scription of the mathematical process that has been followed in de-
veloping the mathematical formulas whose graphical interpretation

has been discussed above.

ii

The frequency-distortion component of tracing distortion is ob-
tained by finding the relative variation with frequency between the

504 M. J. Di TORO [J. S. M. P. E.

amplitude of the recorded fundamental sinusoidal wave (the "cause")
and the amplitude of the fundamental in the traced wave (the
"effect"). The amplitude-distortion component of tracing distor-
tion is determined by finding in the traced curve the ratio of the rms.
amplitude of the second and higher spurious harmonics to the ampli-
tude of the fundamental.

If a mathematical attempt is made to find the traced curve for a
sinusoidal undulation with the endeavor later to find the 2nd, 3rd, etc.,
harmonic components of the traced curve by well known methods of
harmonic analysis (i. e., Fourier Series) u an insurmountable difficulty
is faced. This is due to the transcendental nature of the equations
involved, so it becomes evident that to obtain any solution at all an
approximate method of attack must be resorted to. The real prob-
lem thus becomes one of analyzing a recorded curve that is sufficiently
nearly sinusoidal, from the standpoint of low harmonic content, to
preserve the essence of the problem and at the same time provide a
recorded curve of a shape amenable to analysis. Upon realizing that
about the only two curves for which the traced curve comes out ana-
lytically simple are the circle and the straight line, this fact is made
the basis upon which the solution of the problem rests, by the expe-
dient of approximating the sinusoidal recorded curve by straight lines
and circles.

Curve 1 of Fig. 6 represents a hill-and-dale recorded undulation
of approximately sinusoidal shape composed of straight inclined lines
and circles. The traced curve 2 is the path of the center of the re-
producer stylus, and is assumed identical with the path of the center
of a circle rolling along the base or recorded curve 1. Curve 2 is also
composed of straight lines and circles and will approach and ulti-
mately coincide with curve 1 as the stylus radius approaches and,
ideally, becomes zero.

Now it is clear that to preserve the essence of the problem the re-
corded curve 1 should deviate only slightly from a sinusoidal wave-
form, in the sense that the amplitudes of its harmonic components
should be only a few per cent of the amplitude of the fundamental.
Letting bn represent the amplitude of the nth harmonic component of
curve 1, then bn is a function of a, and, in consequence, a judicious
choice of a may be made that will result in desirably low relative am-
plitudes of the harmonics (i. e., in small values of b*/blt bz/bi, etc.}.
(This specific choice of the value of a also determines the value of c.)
The functions bn are determined by an application of the well known

Nov., 1937]

DISTORTION IN REPRODUCTION

505

Fourier Series expansion to curve 1. It is found that the processes
required to do this are simplified if the circular portions of curve 1 are
further approximated by parabolas, as shown in Fig. 7, and an analy-
sis made of the resulting derivative curve of curve 1. This deriva-
tive curve is then composed simply of straight inclined and horizontal

FIG. 6. Circular and straight-line approximation to sinu-
soidal recorded undulation (1) and to path of reproducer
stylus (2).

lines. Term-by-term integration of the Fourier series expansion of
this curve leads to the expression :

- o)

"sin Trwa sin irw(a

m(a + V,n

Va -a

(3)

where n = the order of the harmonic.

By choosing a = l/3, then bz = b± = 66 = etc.= 0, and b6/bi = 0.008,
h/h = 0.003, etc. For this value of a, curve 1 is very close to being
purely sinusoidal in wave-form inasmuch as it contains no harmonic
terms of order lower than the fifth, the magnitude of the latter rela-
tive to the fundamental being less than one per cent.

In view of the foregoing, the presence of 2nd, 3rd, and 4th harmonic
components in the traced curve 2 of Fig. 6 is then an indication of

506 M. J. Di TORO [J. S. M. p. E.

spurious harmonic formation due entirely to tracing distortion. In-
dicating by Bn the amplitude of the wth harmonic component of the
traced curve 2, it is found, by a process similar to that used in finding
bn, that BJBi is a function of only a single dimensionless parameter
P, the tracing factor mentioned in Section /, and whose physical
significance is shown in Figs. 6 and 7. Thus:

for * * ' tf •/* Bn = in

for P ^ •/.,

(Comparing 4 and 3, it is seen that for P = 0 = R, Bn = bn.) The
functions BJBi are graphically shown in Fig. 2 of Section /. As the
stylus of a velocity-responsive reproducer goes through a motion
whose nth harmonic component is represented in amplitude by Bn,
the reproducer output will magnify these components of the stylus
motion by the order of the harmonic, in view of the proportional in-
crease in responsiveness with increase in frequency of a velocity-
responsive reproducer. If Bn' represents the amplitude of the nth
harmonic in the output of such a reproducer, then it is obvious that
B'JB'i = nBJBi. The B'JB'i functions are graphically shown in
Fig. 3.

The magnitudes of the functions BJB} for specific values of the sys-
tem parameters, A , F, R, and V may also be computed from a har-
monic analysis of the graphically determined traced curve of an exact
sinusoidal recorded undulation. This has been done, in order to
substantiate the closeness to the exact curves of the approximate
traced and recorded curves used in the mathematical analysis just
described. Fig. 8 shows a comparison between the results attained
by this graphical method and those attained from the mathematical
analysis. A well known numerical method of harmonic analysis
has been used in obtaining the various components of the graphically
determined traced curve.12 The calculations extend over wide ranges
of the dimensionless variables U = A/\ and W = R/\, where X =
the wavelength = V/F. U is the amplitude of the recorded undula-
tion in number (or fraction) of wavelengths, and W is the radius of
the reproducer stylus in number (or fraction) of wavelengths of the
recorded undulation. It is noted that since the complete behavior

Nov., 1937]

DISTORTION IN REPRODUCTION

507

of the system is determined by the tracing factor P, and that from
equation 4, P is a function of A/\ and R/\, it follows that the latter
two dimensionless variables are sufficient to define the system com-
pletely.

The traced curve of a complex recorded undulation composed of
two or more different fundamental frequencies contains not only the
2nd and higher harmonics of the component recorded frequencies,
but the sum and difference (and other multitudinous combinations)
of frequencies that generally bear a discordant musical relation to the
recorded fundamental frequencies, and are in consequence respon-

PARABOLIC APPROXIMATION TO
CIRCULAR TRACED CURVE

CIRCULAR TRACED CURVE

PARABOLIC APPROXIMATION TO
CIRCULAR RECORDED CURVE

- CIRCULAR RECORDED CURVE

DERIVATIVE CURVE OF
CIRCULAR TRACED CURVE

STRAIGHT LINE APPROXIMATION AND
DERIVATIVE CURVE OF PARABOLIC
TRACED CURVE

DERIVATIVE CURVE OF
CIRCULAR RECORDED CURVE

STRAIGHT LINE APPROXIMATION AND
DERIVATIVE CURVE OF PARABOLIC
RECORDED CURVE

P-D/(V«)

FIG. 7. Graphical description of mathematical approximations.

sible for the raucous nature of the amplitude-distortion component
of tracing distortion. Now, the very non-linear property of this
system that gives rise to these discordant frequency components is
responsible also for the generation of the 2nd and higher harmonics
in the reproduction of a single-frequency recorded undulation. It is
thus clearly evident that a measure, in the traced curve of single
frequency, of the ratio of the rms. 2nd, 3rd, etc., harmonic components
to the fundamental frequency component is also a measure of the
raucous characteristic of the system due to the amplitude-distortion
component of tracing distortion. In an experimental test in which a
complex recorded tone composed of two different frequencies was re-
produced, it was actually possible by the use of suitable band-pass

508

M. J. Di TORO

[J. S. M. P. E.

filters to segregate in the distorted reproducer output component
frequencies of the sum and difference frequencies of the two different
fundamental recorded frequencies.

An indication of the analogous nature of tracing distortion to other
more common and perhaps more familiar distorting systems in this
respect may be of interest. In a triode working in its region of
curved static characteristics, the relation between the distorted varia-
tional plate current i and the variational grid voltage e is

i = cie + ctf2 + etc (5)

where the c's are parameters dependent upon the form of the curved
characteristic of the tube and upon the plate load impedance. When

100

p

U'A/X

W=R/X

-^

-^

V-XF ' 6AF

0«5
120
130
204

028
026
OSI
.OSI
OSI

0

X

<

g

0

t

3

60
30
40
30
20
10

30
40
30

to

10
0

A

5

593

214
573
107
391

OSI

III
III
222

A

^(

1 — i

\

^B

g

x.

ffl

1.36
.196
255
4 17

222
222.
.222
222
.222

ca
t

FUNDAME NTAHFROM FIG. 3
2ND HARMONIC —^.
3RD HARMONIC ^

i —

—

"^

--^

•^s,

^^

.

^v^

••

-,

"\

^*\

s

s

•

II

_ \

J

i

.-

•

t"

;\

x-

\ ^

1 u

„.•

—

•

-*•

—

h-

-/

—

--i

~ •

^T

^

, *

•*"

t "

i

,

.-if

P^

f

**

*A~

*•* '

*-

...

'

1.5 20 3.0 4.0 8.0 T.O 10.

VALUES OFP

FIG. 8. Comparison of results obtained from mathematical harmonic
analysis of parabolic and straight-line approximation to traced curve
(dash-line curves, as obtained from Fig. 3), and from numerical harmonic
analysis of exact traced curve obtained graphically (shown by points).

this plate load impedance is a capacity C whose reactance is large
compared with the internal plate resistance of the tube, the following
results are obtained: Upon applying a sinusoidal voltage to the grid
of the form e = E cos 2ir Ft, the ratio of the magnitude of the second
harmonic component to the fundamental component on the right side
of equation 3 has the form :

(KC)F*E (6)

where K is a constant dependent upon tube curve characteristics.

Nov., 1937] DISTORTION IN REPRODUCTION 509

The corresponding ratio for the amplitude-distortion component of
tracing distortion may be obtained from a series expansion of Bz/Bi,
where B\ and B% ars defined by equation 2. It can be shown that for
small values of P the result of this series expansion is an expression
proportional to P Hence, for (V/QAF)2 ^> 1, the analogous ex-
pression to 4 in tracing distortion is, within a numerical constant,

(R/V*) F*A (5)

It is seen that in both distortion systems the per cent 2nd harmonic
is proportional to the "cause" ( = E in the tube analogy and A in the
recording system) and proportional to F2, the square of the frequency.
The author is greatly indebted to Mr. O. M. Dunning, for his useful
suggestions regarding the subject matter and for his encouraging
attitude and aid in writing this paper. Thanks are also due to Mr.
T. M. Edison for his interest and comments.

REFERENCES

1 MclLWAiN, K., AND BRAiNERD, J. G. : "High-Frequency Alternating Cur-
rents," 1st Ed., John Wiley & Sons (New York, 1931), p. 135.

2 SHEA, T. E., McNAiR, W. A., AND SUBRIZZI, V. : "Flutter in Sound Records,"
/. Soc. Mot. Pict. Eng., XXV (Nov., 1935), No. 5, p. 403.

3 KELLOGG, E. W. : "A Review of the Quest for Constant Speed," J. Soc. Mot.
Pict. Eng., XXVHI (April, 1937), No. 4, p. 337.

4 MAXFIELD, J. P., AND HARRISON, H. C.: "High-Quality Recording and Re-
producing of Music and Speech," Trans. A. I. E. E., 45 (Feb., 1936), No. 2, p. 334.

5 KELLOGG, E. W. : "Electrical Reproduction from Phonograph Records,"
Trans. A.I.E.E., 46 (June, 1927), No. 6, p. 903.

6 FREDERICK, H. A.: "Vertical Sound Records: Recent Fundamental Ad-
vances in Mechanical Records on Wax," /. Soc. Mot. Pict. Eng., XVIII (Feb.,
1932), No. 2, p. 141.

7 BRYSON, H. C.: "The Gramaphone Record," 1st Ed., Ernest Benn, Ltd.
(London, 1935).

8 FLETCHER, H.: "Speech and Hearing," 1st Ed., D. Van Nostrand & Co.
(New York, 1929), p. 79.

9 C ^OK, E. D.: "The Aperture Effect," /. Soc. Mot. Pict. Eng., XIV (June,
1930), 1 'o. 6, p. 650.

10 MERIT, P.. AND GRAY, F.: "A Theory of Scanning and Its Relation to the
Characteristics of the Transmitted Signal in Telephotography and Television,"
Bell Syst. Tech. J. (July, 1934), p. 464.

11 SOKONIKOFF, I. S AND E. S. : "Higher Mathematics for Engineers and
Physicists," McGraw-Hill Book Co. (New York, 1934), p. 134.

12 GROVER, F. W.: "Analy.-'s of Alternating-Current Waves by the Method
of Fourier, with Special Reference 10 Methods of Facilitating the Computations,"
Reprint No. 203, Bull. Nat. Bur. Standards, 9 (May 15, 1913).

THE OBJECTIVE QUANTITATIVE DETERMINATION OF
THE GRAININESS OF PHOTOGRAPHIC EMULSIONS*

A. GOETZ AND W. O. GOULD *<

Summary. — A graininess meter as an instrument for objective and quantitative
determination of density fluctuations of photographic emulsions is described. The
instrument, specially designed for the purpose, produces a micro photometric record of a
uniformly exposed area in terms of relative transparency fluctuations (AT/rm) (Tm —
mean transparency). The resolving power of the optical system is greater than the
individual grain size, so that granularity as well as graininess is recorded. Unlike
the usual microphotometric records, the records are produced in such a way that they
can directly undergo a process of partial integration in a photoelectric integrator de-
signed for the purpose. Thus the distribution of the areas occupied by transparency
fluctuations as a function of the magnitude of the deviation is determined. In addi-
tion, the sum of the fluctuations can also be measured. The distribution function is
found to be predominantly a Gaussian probability function (C/G)e~(-x/G)*, upon
which an exponential distribution function (C/G}e~^x^ is superimposed. The
graininess constant G is defined as the inverse rate of decline of the occurrence of rela-
tive transparency fluctuations with the deviation from average transparency. A con-
struction of the integrator, though provisory, is given which allows direct readings of
the numerical values of G without involving calculations.

The graininess meter has been applied to the measurements of the graininess^density
function and, furthermore, to the effect upon the emulsion by the variation of the mode
of development. In addition, quantitative determinations of the increase of the graini-
ness in contact prints with respect to the graininess qualities of the negative ma-
terials from which the print is made are described.

(I) INTRODUCTION

Until recently the graininess of photographic emulsions has been
measured and defined in entirely subjective terms, a procedure justi-
fied in most cases inasmuch as the graininess was only subjectively
realized. In this sense the definition of graininess by Jones as "the im-
pression of inhomogeneity felt by an observer in viewing the enlarged
projection of a photographic image" is correct. In addition to pro-
jections of the photographic image for the subjective realization by an
observer (motion picture projection, enlargements of photographic

* Presented at the Spring, 1937, Meeting at Hollyv/ood, Calif. ; received
May 15, 1937.

** California Institute of Technology, Pasadena, Calif.
510

DETERMINATION OF GRAININESS 511

negatives) the graininess affects an increasing number of applications
wherein the limited resolving power of an emulsion is objectively real-
ized, as, for instance, in microphotometry and sound-track recording.

General experience shows that the graininess varies greatly with
different emulsions, and for the same emulsion with its processing;
and, furthermore, that it is invariably aggravated by printing and
duplication to magnitudes that critically diminish the applicability
of the emulsion. Moreover, concerning the physical causes of the
graininess, it is known that the granularity, or average size of the
grain (i. e., the reduced silver particle in an emulsion) is far from being
the only determining factor. Therefore, to find ways and means of
determining the graininess of a particular emulsion by objective
methods and to define it in definite terms such as density, gradation,
sensitivity, etc., has grown into a definite necessity.

Accordingly, a number of papers have been published in recent
years on the subject from the theoretical and the practical points of
view, of which the work of van Kreveld1'2'3 is the most outstanding
and goes partly along the same lines as ours, although developed
simultaneously and independently.

(II) THEORETICAL CONSIDERATIONS

Consider a photographic emulsion uniformly exposed and developed
and having a density D. The area A of the emulsion is investigated
with a magnifying device (projection or microscope) where A is large
enough for the measurement of a statistical average : that is, where
it contains within its boundaries all the possible density fluctuations
occurring. In addition, a fraction of A called a is investigated with
a magnifying device of high resolving power. A and a are illuminated
and the transmitted light is measured and recorded by two indepen-
dent photoelectric systems. If the emulsion is then moved with re-
spect to the optical systems, the light transmitted by A will remain
constant (if D is constant and A is sufficiently large), but the light
transmitted by a will fluctuate because of the inhomogeneity of the
emulsion, provided that a is small enough and the resolving power of
the microscopic system sufficiently large. The light that reaches
the photocell of A is obviously equivalent to the mean transparency
Tm of the emulsion, whereas the light that reaches the photocell of a
represents local transparencies that will obviously fluctuate around
the average value Tm during the motion of the film. If the size of
each fluctuation is called Ar, the sum of all fluctuations Tm ± AT,

512

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

if recorded over a sufficiently large area of the film, must equal Tm.
Thus a record of the type shown in Fig. 1 will be obtained, where the
ordinate denotes T and the abscissa the length L of the a-strip re-
corded; the dotted line Tm represents the record obtained from A, the
zigzag line the record from a.

If emulsions of different densities (and, accordingly, different Tm)
are used, and the intensity of the illuminating light is so adjusted in
each case that the light transmitted through A is the same,
the size of A T is made to refer always to the mean transparency;
that is, the amplitudes of the fluctuations from a are recorded in
terms of AT/Tm. As the density is related to the transparency by
D = In 1/r, the measurement of the relative transparency fluctua-

a

o

L.

FIG. 1. (Left) Schematic microphotometer record: L, length of

record; T, transparency; TM average transparency.
FIG. 2. (Right) Different forms of fluctuations of equal area.

tion Ar/r corresponds in good approximation to the absolute density
fluctuation which, according to Fechner's law, is the true representa-
tion of the visual impression of the observer caused by the graininess. *
The value of the graininess of a particular emulsion for a certain
density could then be obtained simply by the measurement of the
area circumscribed by the A T curve (Fig. 1), i. e., by:

LT

(L

J

U)

which is the average deviation. This, however, may not be a true

* The authors' attention has been drawn to this particular point by the Agfa
Research Laboratories in Wolfen, Germany, to whom they wish to express their
obligation, also for constructive criticism on a number of other points in this para-
graph.

Nov., 1937] DETERMINATION OF GRAININESS 513

representation of the subjective impression caused by such fluctua-
tions, as the shape of the average fluctuation, and not only the area
occupied by it, influences the graininess impression. In Fig. 2 three
different shapes of thinkable deviations are indicated, which all oc-
cupy the same area and which accordingly would result in the same
average deviation. It is, however, obvious that the type I would
give a very much larger impression of inhomogeneity than // and
///.* A way out of this difficulty would be to weigh the amplitudes
of the fluctuations in a non-linear fashion ; that is, to average instead
of as in equation 1 , thus :

(»> l~) (2}

LTn,

It has been suggested in analogy to certain mechanical and electrody-
namic methods to choose n = 2, but the correct value would have
to be determined by physiological tests to render the choice of n other
than arbitrary.**

In addition to the indeterminacy of the values of graininess thus
obtained (due to the arbitrary choice of the value of n) the method
involves the use of a planimeter, which can prove rather cumbersome
when large numbers of records have to be analyzed.

A different and very ingenious process has been developed by van
Kreveld,2'4 which consists of a direct measurement of the mean value
of the density fluctuations by passing the emulsion simultaneously
through two microphotometric systems so arranged that the mean
differences of the fluctuations of closely neighboring regions are in-
dicated. This method has given good results, which are analogous
to the subjective impression of the graininess, and it is thus very
valuable also for practical purposes.

* Type I, for instance, would be realized in an emulsion of large granularity
and small density, whereas type /// could be produced by a fine-grain emulsion of
high density.

** The ratios of height to width in Fig. 2 are, for/, 10 : 1; for //, 3.16 : 3.16;
for ///, 1 : 10. The values obtained by the integration (eq. 2) for different values
of n are as follows:

n I II III

111 1

2 1 0.316 0.1

3 1 0.1 0.01

514 A. GOETZ AND W. O. GOULD [J. S. M. P. E.

The method for the determination of graininess described in this
paper differs from the above mainly in that it is based upon the
measurement of the actual distribution of the fluctuations over the
range of occurring transparencies, which, in our opinion, is most im-
portant for the study of the particular nature of the grain accumula-
tions in an emulsion, and which permits the establishment of a mathe-
matically simply denned constant descriptive of the graininess quali-
ties.

It is obvious that the subjective impression as well as the resolving
power of an emulsion is in direct relation to the probability of the oc-
currence of deviations AT" from the mean transparency as a function
of their magnitude. It is also obvious to expect that this probability
function II will decline with increasing values of AT", so that the
general relation can be expressed as :

n — ^.f \Tm-G / (n\

— 7, C W

where C, G, and n are constants descriptive of the function. C/G
refers to the value of II if the exponent equals 0, that is, if no devia-
tions from Tm occur. The constant G determines the rate of decline of
the occurrence of relative transparency fluctuations with increasing am-
plitudes of the fluctuations AT; that is, the "flatness" of the distribution
curve of the fluctuations. As will be later discussed in more detail,
G is equivalent to the graininess constant. The constant n is not de-
terminable without experimental measurements, but once deter-
mined, it becomes, together with C, a universal constant for all
classes of emulsion that follow this particular type of distribution.
It can safely be assumed that the value of n lies between 1 and 2.
In case of n = 1, equation 3 obtains the form :

_
n = 1 e Tm'G (3a)

In the case of n = 2, equation 3 changes into :

H - —r- • e TmG' (3b)

Lr\/ IT

which is the well known Gaussian probability function that van
Kreveld2 has reported to be valid for the distribution of the trans-
parency fluctuations. In view of the fact, "however, that the de-
termination of the validity of a statistical law involves the measure-

Nov., 1937]

DETERMINATION OF GRAININESS

515

ment of a very large number of individual occurrences, which so far
has not been obtained, and due to our own results, the off-hand as-
sumption of the applicability of the Gaussian law to the graininess
problem needs experimental justification in each individual case.*

If II is to be evaluated from a microphotometric record (Fig. 1)
it is obvious that with the frequency of occurrence of fluctuations of
a certain amplitude, the area of the record occupied by them is taken
into consideration. This amounts to a summation of the (small)
areas a included by each fluctuation for a certain value of AT/Tm
over a given length of the record.

A practicable procedure for determining the distribution of these

+AT

-AT

FIG. 3(a). Microphotometer record in which the
blackened area is proportional to the fluctuation area; (b)
type of blackening used for the determination of graini-
ness.

areas is demonstrated in Fig. 3(a) where a record similar to Fig. 1
is blackened in order to distinguish the regions occupied by fluctua-
tions. If this record is covered except for a horizontal slit of small
width, and if this slit is moved along the T axis, the "amount of black"

* It may be pointed out that the question of the validity of the probability
law is of much more than casual importance as far as the actual nature of the
grain coagulation in an emulsion is concerned. It is realized from the fact that the
probability function (n = 2) holds only and always in such cases where the oc-
currenc0 of grain complexes is only accidental, that is, causeless. If, however,
there exists a cause, that is, forces of a physical nature which affect the approach
or the separation of individual grains, the probability law cannot be expected to
hold any more strictly; hence its validity or nonvalidity is indicative of the ex-
istence of such forces.

516 A. GOETZ AND W. O. GOULD [J. S. M. p. E.

exposed through the slit indicates for each position (i. e., for each
value of T) the sum total of fluctuations X)° = 2 that are larger than

AT

a certain value of AT" indicated by the position of the slit. At T =
Tm the area exposed has to be largest ( = a0). A variation of this
method actually used because of the simplicity of recording is shown
in Fig. 3(6), where the whole area below the recorded line is black-
ened.* The slit moving from small values of T toward Tm will ex-
pose first only black; then increasing amounts of white; and at Tm
the black areas will equal the white areas. (This condition is inde-
pendent of the size, or even the presence of fluctuations for a finite
width of the slit!) If the slit is moved beyond Tm the "amount of
black" will decrease until only white is left. Thus 2 is proportional
to the "amount of black" for T > Tm and to the "amount of white"
for T < Tm.

The x axis of the distribution curve is thus identical with the T
axis in Fig. 3 (a, 6), where T = Tm for x = AT" = 0. Thus the x
scale presents values of AT/Tm; e. g., as x is expressed in frac-
tions of Tm, T = 2Tm for x = 1. According to the aforementioned
relation, the x values correspond thus to the absolute size of the den-
sity fluctuations. The ordinate of a diagram thus obtained is rep-
resented by the 2 axis, the units of which represent the sum of fluctua-
tions larger than a given value of AT". It is obvious that the resulting
function will lie symmetrically to Tm, as fluctuations of transparency
values less than Tm are as frequent as those larger than Tm, this being
the definition of Tm. Hence it is necessary to consider only one-
half of the curve. The S (x) function thus obtained is in close relation
to the distribution function in equation 3, as the former represents
the integral function of the latter :

where C is chosen so that for a given value of n :

GJo
For the two aforementioned values of n the valuation of the inte-

* It is seen the record thus obtained is similar to the sound-track of the variable
area sound recording system.

Nov., 1937]

DETERMINATION OF GRAININESS

517

grals is simply accomplished, being obvious for n = 1. For n = 2,
2 " '^'*-«

where <l> is the well known probability integral, so that in combination
with 4 and 4a:

?:(*)n=2 = 1 - * (4c)

which is easily obtainable in tabulated form. The shape of the S (x)
function for the two respective values of n is shown in Fig. 4 (a) for

1.0
08

0.6
0.4
0.2

T

0.5 1.0 1.5

0.5 1.0 1.5

1.0
0.8
0.6
0.4
0.2

0.5 1.0 1.5

0.5 1.0 1.5

FIG. 4(a). Integral functions ~S,(x) for a simple expo-
nential (n = 1) and a Gaussian (n = 2) distribution,
(G = 1); (b) Simple exponential and Gaussian distribu-
tion function derived from curves in (a); (c, d) Dis-
tribution functions for G\ = l/tGz.

values of C to satisfy equation 4a and for the same value of (G = 1).
Fig. 4(6) shows the actual distribution curves obtained by differentia-
tion of the curves of Fig. 4(a).

The function for n = I remains unchanged, whereas the function
for n = 2 represents the well known probability curve. The inter-
section with the II axis differs by the factor 2/\Ar. For small values

518 A. GOETZ AND W. O. GOULD J. S. M. p. E.

of x the probability of occurrence of fluctuations is smaller for n = 1
than for n = 2, whereas the opposite is true for large values of x;
the probability is the same for a value of x/G = 1.11.

The influence of G upon both functions is obviously such that with
an increasing G the curves grow flatter and their intersection with the
n axis at Tm grows smaller (<~l/(/). The variation of the area with
G can easily be demonstrated in a manner shown in Fig. 4(c) and
(d), where the same functions are shown as in Fig. 4(b), however,
each for two different values of G (G\ = 1/2 G2). It appears that
the shaded area included by the curve for Gi is equal to that included
by the curve for Gz if the lower limiting x value of the former is one-
half that of the latter. Thus the following definition of G becomes
obvious : the probability of occurrence of amplitudes of relative trans-
parency fluctuations larger than a deviation given by G is a constant;
which leads directly to another form of definition of G, inasmuch as
G indicates directly the lower limit of deviations from Tm, the sum total
of which occupies a defined fraction of the total area of the emulsion.

From this the units of G are derived as follows: for G = x = 1
equation 3a becomes :

H(x)n_i = :&(*)„_! = l/e = 0.368 (5a)

in case n = 1 ; that is, 36.8 per cent of the area of the emulsion is oc-
cupied by fluctuations AT> Tm.

For n = 2, the unit of graininess is obtained from equations 4b and
4cas:

S(*)n-2 = 1 - «£,_i = 0.157 (56)

that is, fluctuations with the above-given lower limit cover 15.7 per
cent of the area. For G = 0.1 the lower limit of the fluctuations
changes accordingly from Tm to 0.1 Tm*

The numerical values of G thus obtained will depend upon the
scanning area a (not to be confused with the area used in the above
definition of G!) , as long as a is large compared with the size of a
single constituent of a fluctuation, that is, a single grain. As the
realization of more favorable conditions meaning sufficiently small

* The choice of the magnitude of the area used for the definition of the units
of G for practical purposes affects, of course, only the absolute and not the rela-
tive values (neither the degree of descriptiveness nor subjective impression) and
is thus entirely free, and only bound by convention. The area used in this
paper has the advantage of a particularly simple relation to the e functions,
which simplicity, however, is to all practical future purposes of no importance.

Nov., 1937]

DETERMINATION OF GRAININESS

519

values of a, is difficult, since the sensitivities required would render
the instrument too delicate, considerably larger areas have to be
chosen, which, if used in the determination of G render its value
dependent upon a. For practical purposes an area of constant
size called the "standard-integer" has been adopted which represents
a compromise between manageable sensitivities of the recording
system and a desirable small dependence of G upon a. The mag-
nitude of a chosen for practical purposes is of the order of 10V2.

FIG. 5. Optical and electrical arrangement of the graininess photometer.

The dependence upon the resolving powers of the electrical and
optical systems will be discussed below.

(Ill) THE GRAININESS METER

The operation of measuring the graininess involves two different
steps: one in which a microphotometric record of the emulsion is
taken, the other in which the record obtained is evaluated in terms of
the G values of the distribution curve.

(a) The Graininess Photometer. — The instrument built for this
purpose is in principle a microphotometer, although a number of
costly devices present on the usual microphotometer are omitted as

520 A. GOETZ AND W. O. GOULD [J. S. M. p. E.

being unnecessary for this particular purpose, whereas other devices
are added. The apparatus divides itself into three different com-
ponents (Fig. 5). First, the microscope with camera and illuminating
system; second, the photoelectric cell with electrometer and its
auxiliaries; third, the mechanical driving system with the recording
drum.

The microscopic system consists of the microscope tube MI with the
objective 0\ and eyepiece which fits with a loose collar onto the
camera C. The emulsion under investigation is mounted between
slide and cover glass SL, and is clamped on the rotating stage ST.
The illumination system on the microscope is the usual one consisting
of the condenser lens C\, the diaphragm Di, and the plane mirror.
The constancy of illumination is of great importance, and also the
intensity of light has to be adjustable within a wide range ; accord-
ingly precautions are taken. The light-source is a tungsten arc LI
headed by condensers Cz and a water-cell. The arrangements for
constancy of the arc are obvious from the drawing, consisting of a
number of rheostats and two iron-hydrogen wire resistances.

The image produced by the eyepiece of the microscope MI is pro-
jected upon a plane in the upper end of the camera C which is divided
into two sections. The right section consists of a ground-glass plate
PI. This image is reflected on the mirror Q which is mounted at a
45-degree angle above PI and which is open to the observer through
the shaft SH. Thus it is possible to focus the image of the emulsion
upon PI. The left half of the camera is occupied by a high-sensitivity
photoelectric cell, either of the surface or the layer type (the arrange-
ment used for the former is shown in Fig. 5). This arrangement
renders it possible to have a known section of the image acting upon
the photoelectric cell whenever the image is in focus upon PI. In
order to vary this section diaphragms, D3, of different apertures can
be put in front of the photocell in the plane of PI. The areas of the
diaphragm being known, thus permit a known variation of the section
of the image.*

In order to be able to integrate over an area of emulsion sufficiently
large for a statistical average, simultaneously with the measurement
of the small area on PH the device shown in Fig. 6 is used. The illus-

* The diaphragm and the optical magnification of the microscopic system de-
termine the "standard integer." For the measurements taken this area was
870M».

Nov., 1937] DETERMINATION OF GRAININESS 521

tration shows the lower end of the microscope tube Mit into which is
inserted a vertical-illuminator consisting of a very thin clear glass plate
P3 inclined 45 degrees to the optical axis. A small fraction of the light
that comes through 0\ is thrown upon the layer cell CL, which, in
turn, is connected to the galvanometer G\. If emulsions of different
densities are used, the intensity of light is regulated so that the gal-
vanometer shows always the same deflection, which then means that
the transparency fluctuations recorded by PR (Fig. 5) are proportional
to AT/Tm. In case of the use of a surface cell for PR, a string elec-
trometer is used as indicator, which is built into the aforementioned
camera and is connected with PR through highly insulated wiring of
small capacity. The electric connections between the cell and the
electrometer are obvious from the drawing.

The electrical adjustments for the electrometer are made as follows :
in order to obtain a linear relation between the potential at the string
St and its deflection, a large distance between the plates Pt is used,
necessitating accordingly a high plate potential which is supplied by a
set of dry batteries (225 volts). In order to adjust the potential of
the plates a potentiometer arrangement was effected by connecting
the slide-wire resistance R6 (25,000 ohms) and #7 (500,000 ohms)
in series as shown in Fig. 5. One end of the battery and the movable
contact of R7 are connected to the plates Pt so that R^ serves for the
rough and R* for the fine adjustment of the plate potential, i. e., the
sensitivity of the electrometer.

In order to facilitate the exact adjustment of the ground potential
with reference to the plate potential, a second set of resistances R$
(500,000 ohms) and R9 (25,000 ohms) are put across the plate po-
tential, that is, in parallel to the section of RI in use. The moving
contact of R% is connected to the ground, and it is thus possible by
using R8 as a rough and R9 as a fine adjustment to bring the ground
potential into exactly the same plane where the string is at rest when
no potential is applied.

Since the electrometer is supposed to indicate the current of the
photoelectric cell a gound leak R& (120 megohms) is inserted. For
the protection of the string in case of contact with one of the plates,
the protective resistances Rw (10,000 ohms each) are inserted in the
plate circuit. The potential for the photoelectric cell (135 volts) is
supplied by dry-cells.

An image of the string is projected by means of an illuminating
system (La, C4, C6) and the microscope system (02, microtele-

522 A. GOETZ AND W. O. GOULD [J. S. M. P. E.

objective ; MC) micrometer scale in the eyepiece of M2; total reflecting
prism, PR) partly upon the screen of a recording drum covered with
sensitized paper through the cylindrical lens Lz. The photographic
record obtained in this way shows the path of the string as a fine
white line upon a dark background. For the later evaluation of the
record it is, however, necessary to obtain a record of the type shown
in Fig. 3 (6) . In order to render manipulation of the record (blackening
and bleaching) unnecessary, a layer cell can be used for PH in Fig. 5,
connected to a galvanometer instead of to the electrometer. The
galvanometer has a period less than one second, and its mirror re-
flects the image of a white rectangle of greater length than the width
of the drum upon the slit of the recording drum in such a way that in
a position of the galvanometer corresponding to the zero position of
the string (i. e., AT = 0), the border of the rectangle lies at the center
of the slit of the drum. In this case half the paper is exposed, whereas
the other half remains white; and oscillations of the galvanome-
ter will produce a record of the type of Fig. 3(b) by direct photo-
graphic development.

Simultaneous motion of the slide SL on the microscope stage and
of the recording drum is accomplished by means of an electromotor
MR and a system of worm-gear drives shown in Fig. 5. The speed
of the motor is adjustable and is controlled at the SP speedometer.
The ratio between the speed of the recording drum and the actual
velocity with which the slide passes the objective is given by the
distance between the center of rotation between the stage ST and
the optical axis of the microscope, and is adjusted by means of center-
ing screws on the stage which permit regulation of the speed ratio
between the image and the recording durm. The axle of the record-
ing drum DR has a separate coupling with the worm-gear drive W*
such that the drum can be rotated independently of W3 in order to
adjust the starting point on the record.

As was shown in the previous theoretical considerations, the am-
plitudes of the fluctuations recorded must be proportional to AT/Tm,
and it has already been stated that the varying densities of emulsions
are compensated for by adjusting the light-intensity so that the
amount of light transmitted by the emulsion is kept constant. As
the sensitivity of the electrometer (or galvanometer, in case of the
use of a layer cell) remains the same throughout, and the instruments
are used only over deflections for which the sensitivity is closely
linear, the amplitudes recorded are proportional to ^T/Tm. In

Nov., 1937]

DETERMINATION OF GRAININESS

523

order to calibrate the deflections in terms of fractions of Tm, the
following method is used: The diaphragms D3 (Fig. 5) used for
the measurements exist in duplicates, one of which (.4i) is made 5 to
10 per cent larger than its partner (A0) actually used in the measure-
ments. The areas of A0 and A\ are measured by projection through
a magnifying apparatus, and thus the ratio is exactly known. Then
the diaphragm with the aperture AQ is introduced into the camera
and the illumination is adjusted to Tm as described above. The
ground adjustment is made to bring the image of the string to the
center point of the scale. Then A0 is replaced by A\ and the de-

6.

FIG. 6. Device for the measurement of TM: 0\,
microscope objective; P3, clear thin glass plate; CL,
boundary layer photocell; G\, galvanometer.

flection d (in mm.) of the electrometer fiber is measured. Then the
calibration of the x axis expressed in per cent of Tm per mm. scale
(right and left of zero) is obtained by :

(6)

The total sensitivity 61 of the graininess photometer depends of
course not only on 5A but also on JT where JT is the light-intensity
that enters the microscope for Tn. Thus the upper limit of S is
given by the largest JT which can be used and the largest electrome-
ter or galvanometer sensitivity for which the scale is still linear.
For a light-source of given intensity, JT is given by the maximum
intensity that passes an emulsion of the smallest used transparency.

524

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

(6) The Graininess Integrator. — In order to evaluate the graini-
ness constant from the record so far obtained, it is necessary to sum
up the areas occupied by the fluctuations for each value of AT. The
practical realization of this operation follows closely the process out-
lined previously : The apparatus used for this, shown in Fig. 7, con-
sists of a light-tight box divided into two compartments A and B,
which are light-tight from each other except for the short-focus ob-
jective 0. The record R obtained on the graininess photometer is
put into a frame opposite the objective on the wall of the chamber A .
This record is illuminated by diffuse light coming from a number of
symmetrically arranged light bulbs L, L. . . . A tube T protects the
objective O and the chamber B from direct incidence of light from the

6 fe

7

FIG. 7. Schematic view of the integrator: R, record;
S, diaphragm; T, tube protecting objective O; C,
photocell; L, incandescent lamps; G-lt galvanometer.

bulbs L. A diffuse image of the record is obtained by means of the ob-
jective 0 in the chamber B on the layer cell C. In front of the record
is a black plate with a slit in the center which extends over the
length of the record. The slit is fixed with reference to the objective,
and the position of the record can be read on a scale (x scale) . The
deflections of the galvanometer are then, for each position of the record,
proportional to the "amount of white" previously mentioned, i. e.,
the area either occupied or not occupied by fluctuations, depending
upon whether the black or the white side of the record is exposed.
The galvanometer is calibrated by exposing the photocell C once
with an unexposed sample of the recording paper through the slit,
and once with a sample of completely exposed paper. In the first
case a deflection Jw, in the second, JB, will occur (due to incomplete
blackness). If, then, a record is placed behjnJ the slit and moved

Nov., 1937] DETERMINATION OF GRAININESS 525

along the x scale, a center position will be found in which the galva-
nometer deflection will correspond to V« (Jw + JB) = Jm- This
position of the record on the x axis corresponds to Tm, as the region
exposed here is by definition equally occupied by black and white
independently of the presence or the size of fluctuations. If the rec-
ord is moved from the Tm position toward white, the current will in-
crease from Jm to J w. The value of Jw will be reached at a position
of the record where no fluctuations are exposed. The same is true
conversely for the motion of the slide in the opposite direction where
the current changes from Jm to JB. If a0 denotes the area filled in
the Tm position by either black or white (which is equal to Vz the
aperture of the slit), and a is the area filled by white for a position on
the x scale < Tm, and Jz is the deflection of the galvanometer, the
following relation holds :

i/r ~ BT^ °r for flo = 1 - = a = y (7)

do l/t(Jw — JB) do

The y scale is thus represented by the scale upon which the deflec-
tions of the (mirror) galvanometer of the integrator are projected.
It is divided into twice as -many units as are desirable for each half
of the scale, e. g., 20 units if a/a0 is to be measured in steps of 10 per
cent,* and if dy is the total distance (mm.) on the scale between JB
and Jw (depending upon the sensitivity of the galvanometer) the
y scale is then divided into intervals of da/2Q, where Jw and JB are
designated as 0 and JM as 1. The divisions on the scale then in-
dicate directly values of a/a0 in intervals of 10 per cent.

The use of the integrator would thus consist in moving the record
from the black to the white side and recording the coordinated values
of both scales. This would involve considerable work, especially in
view of the calculation involved in the determination of G. By proper
choice of the scales this labor can be reduced to one multiplication :

In order +o decide the value of the exponent n in equation 3, the
x and y scales are divided into units that represent each of the two
functions as follows: The x scale is divided into equidistant units,
the distance of which represents, as mentioned before, even fractions
of T/Tm> e. g., per cent. It is obvious that a different y scale is neces-

* It is obvious that the accuracy of this scale should not be greater than the
resolving power of the integrator, which is proportional to the width of the slit.
It may be noted that, aside from the accuracy, the indications of the integrator
are, within wide limits, not affected by the width of the slit.

526

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

sary for each value of w, as its scale divisions F have to represent the
reciprocal inverse function. In general terms, if the distribution in-
tegral function I, (#) = y, Y = l/a(y) so that

-rr . _ _1 tr *-

In

C)

and Fn_2 =

if ip(y) is the inverse function of the probability integral $(
The following table shows some values of these functions.

0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.4
1.6

0.130
0.189
0.240
0.287
0.329
0.368
0.404
0.436
0.490
0.536

0.005
0.018
0.043
0.077
0.116
0.157
0.199
0.239
0.313
0.377

1.8

2.0

2.5

3.0

4.0

6.0

8.0

10.0

15.0

20.0

0.576
0.608
0.672
0.718
0.780
0.845
0.883
0.906
0.935
0.951

0.432
0.479
0.572
0.638
0.724
0.813
0.860
0.887
0.924
0.944

Figs. 8(0) and 8(6) represent the F scales for n = 1 and 2, designed
so that similarly to the total length of the x scale, the length of the F
scale can be chosen to match S of the galvanometer of the integrator.
Since x/G = a(y) or G — x/a(y) — xY, the readings of the two scales
have only to be multiplied for each position of the record in the inte-

FIG. 8. Superposition of the left half of the .y and Y scales for (a) n = 1
and (b) n = 2. The ordinate represents the sensitivity of the galvanometer of
the integrator.

Nov., 1937] DETERMINATION OF GRAININESS 527

grator in order to obtain the graininess constant, which, of course,
must be the same for all positions of one record. In case of an inac-
curate record, a certain scattering of the G values will be observed and
an average has to be taken. From this a chief feature of this method
of evaluating the photometer record can be clearly seen, namely, that
the distribution of fluctuations of all amplitudes is taken into account
for the determination of the value of G. It is obvious that only one
of the two Y scales will give constant values, depending upon the value
of n, and if for the proper Y scale the G values show a small drift in
one direction, a deviation from the distribution function is indicated.
In this way it is possible to separate secondary effects (due to gelatin
or film base) from the systematic distribution.

The integrator can, however, be constructed so that the graininess
constant can be read directly, and that any mathematical operation by
the observer is eliminated. This is accomplished by mechanical
coordination of the x and y scales, as shown in Fig. 9.

In Fig. 9(o) the holder H of the record R is attached to the inte-
grator so that it can be moved with respect to to the plate P (shown
broken) which exposes part of the record through the slit SL by
means of a rack-and-gear drive. The center of the rack R can be
moved against H so that it is possible to adjust the Tm position of
the record to coincide with the center of R. R is driven by one-half
of a gear G, the diameter of which equals 2l/ir, where / is the length
of the rack, equal to the width of the record. The gear G carries a
semicircular disk D of celluloid, the diameter of which is considerably
larger than that of G. The disk lies outside the integrator, and a
section of it is exposed through a horizontal slit S. This slit carries
the y scale upon which is projected the light mark L of the galva-
nometer G2 of the integrator (Fig. 7) .

It is obvious that the length of the slit must be equal to Jw — JB;
thus the galvanometer G2 (Fig. 7) has to be adjusted with its zero
point and sensitivity so that its deflections fall upon the correspond-
ing marks of the scale Sz (Fig. 9a).

The x axis is represented by the direction in which the rack moves,
i. e., from — AT^ to + &TmaI. Due to the sizes of gear diameter
and rack, the disk D will turn <p = 90 degrees when the record moves
over half its width (Fig. 96 shows the position at 45 degrees). During
this process the galvanometer will move from Jm to Jw (or /B).
The angle <p is thus proportional to x. If thus a family of distribution
integral curves is drawn upon the celluloid disk transformed into polar

528

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

coordinates (<p = x, r = y) each curve will represent the locus of the
position of the light mark of the galvanometer, while the disk, and
with it the record, is moved from one end to the other. This, of
course, is true only if the fluctuations on the record follow a distri-
bution law for n values for which the disk was designed. Once the
n value is determined by such trial, the graininess is determined simply
by reading the indication at the curve which the light mark of the

FIG. 9. Schematic view of the indicating apparatus of the integrator:
SI, slit; G, gear; R, rack; D, celluloid disk bearing family of G spirals; L,
light mark of G2; S, slot through which sections of the spirals are visible. A
represents the position for A3" = 0; B for a position half-way between
AT" = 0 and AT" = max.

galvanometer has selected. Fig. 9(6) illustrates this procedure for a
position of disk and record other than Jm.

The shape of the polar curves on D representing the distribution
integral function for n = 2 are shown in Fig. 10. The <p scale is
transformed from the x scale in the following way : Tn the construc-
tion indicated in Figs. 9 (a) and (6), only 90 degrees are available for
the motion of the record from the center to the rim, i. e., for x = Tm,
<f>=0 degrees; for Tm + ^•Tmax, ^ = 90 degrees. &Tmax is given by
the sensitivity of the graininess photometer and by the width of the
record used. If, for instance, the sensitivity of the photometer is
1 per cent of Tm per mm., and the half-width of the record is 50 mm.,

Nov., 1937]

DETERMINATION OF GRAININESS

529

140 per cent of Tm has to correspond to a motion of the record of 48
mm.

The y scale is represented by the radius of the polar diagram, and
the curves are calculated according to equation 4 for different values
of G. Needless to say, two sets of curves have to be used for n = 1
and n = 2 which are simply designed on two different disks made
interchangeable.

(c) The Manipulation of the Graininess Meter. — The above con-
siderations may have given the impression that the manipulation of
the graininess meter is very complicated. It is, however, not more
difficult than the manipulation of a normal recording photometer.

10.

FIG. 10. Family of G spirals on the rotating disk of the integrator,
spiral is the locus of one graininess value.

Each

The determination of the graininess of the emulsion begins with
the adjustment of the sensitivity S of the photometer. Next the
illumination of the specimen is adjusted according to its Tm. Then
the record is taken and developed. If the record was taken with the
galvanometer recording device, the record is ready for integration;
whereas if the string electrometer was used (as was done with the
records described in the following sections), the record must be inked
and bleached. The record is then put into the integrator, and the
sensitivity in the zero position of the galvanometer G% is adjusted to fit
the y scale. The position of Tm is then found and the x scale made to
coincide with it. Then the G spiral selected by the galvanometer is

530

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

noted, which gives G. If the integrator is equipped with x and Y scales
instead of the rotating disk, the x and lvalues are read for a number of
positions of the record, and an average of the product of each pair of
values is taken which then represents G. The operation of the inte-
grator should not take more than three or four minutes for each record
for a trained person, if the scales are used. The use of the disk
shortens the time considerably.

The G values used in the following sections were obtained with the

AT

-.4

Q J.

s

AT

j a.

FIG. 11. x— y diagram of the integrator curves for
three emulsions of different graininess. Each emulsion
is measured in two records in order to demonstrate devia-
tions from the statistical average.

x- Y scales in view of the uncertainty of the nature of the distribution
function.

(IV) THE GRAININESS OF PHOTOGRAPHIC EMULSIONS

The measurements described in the following sections represent
the beginning of a systematic investigation of the graininess prop-
erties of emulsions and of the influence of developer and developing
conditions upon G. Furthermore, the problem of the increase of
graininess due to printing is studied with special regard to the relation
between the graininess of the negative and print. The measure-
ments described in this paper have more the character of a preliminary
survey, as at the present time sufficient material is not available.
The main emphasis was put upon the study of the distribution func-

Nov., 1937]

DETERMINATION OF GRAININESS

531

CVJ

532 A. GOETZ AND W. O. GOULD [J. S. M. p. E.

tion of the relative transparency fluctuations, the knowledge of which
is of fundamental importance for the evaluation of G.

(a) The Distribution Function of A7\ — -A number of graininess rec-
ords were taken with a constant S& and integrated with the use of
the y and x scales. Plotted accordingly, they represent the true
distribution integral function as shown in Fig. 1 1 . From the analogy
of the shape of the curves with those of Fig. 4 (a) it is seen that the
value of n for the distribution curve can not fall far from the values
assumed. The question remains, however, whether the shape of
the curves corresponds to a distribution function that follows the
probability law or is better given by one of simple exponential type.
This can be decided by plotting such observations in a V-x system
with equidistant units for V=a (y), so that Vn_l = Ig (l/y) and
7B_2 = 0(1 — y\ as is done for five samples of different graini-
ness in Figs. 12(o) and 12(6).* In such a coordinate system functions
XX*) = y with a corresponding value of n will be represented by a
straight line.

One could assume from the way in which the observations in Fig.
12(a) fit, for small values of AT, onto a straight line, that the functions
can be described as simple exponential functions (that is, n = 1).
The observations have, however, a tendency to deviate for larger
values of AT in a convex fashion which would indicate lesser graininess
for greater than for smaller deviations from Tm. Besides an inade-
quacy of an exponential function to describe the distribution function,
there could be other different causes for the deviation from the
straight line that actually takes place in the Vn_l— x system as, for
instance, causes due to the experimental set-up.**

It is, however, seen from the curves for the same observations
plotted in the Vn_2— x system, that a distribution function following
the probability law gives for most of the curves a good representation,
whereas some show with this ordinate scale a deviation opposite that
found with the former (Fn_,). Hence one arrives at the conclusion:

* The data used for Fig. 12 come from positive prints and negative emulsions
of different origin and densities. The graininess constants have the following
values : for 7, 0.030 ; for II, 0.049 ; for ///, 0. 1 15 ; for 7 V, 0. 138 ; for V, 0. 192. These
numerical G values, as well as those used in the graininess-density diagrams (Figs.
13, 14, 15), can be reduced to the definition derived from equation 5b for n = 2
by multiplying by the constant proportionality factor of 1.4.

** There are, in fact, several such causes predictable which would all be effec-
tive in a tendency to suppress the smallest T's, -such as the Callier effect and
non-perfect linearity of the recording instrument.

Nov., 1937] DETERMINATION OF GRAININESS 533

The distribution function of the transparency fluctuations is predomi-
nantly a Gaussian probability function upon which a simple exponen-
tial distribution function is superimposed.*

(6) The Influence of the Developing Time on the Graininess of Nega-
tive Emulsions. — Two different emulsions, both of which are used as
negative film in the motion picture industry, were studied with re-
spect to the influence of the time of development. The results are
represented in Fig. 13(a) and (&), where the graininess G is plotted
against the density. Fig. 13 (a) represents a panchromatic emulsion
of high sensitivity, whereas Fig. 13 (6) is taken from a negative emul-
sion of extremely fine grain. The letters A,B and C,D designate the
curves obtained from films that had been developed 12 and 8 minutes,
respectively. In both cases the developer is the same.

First, it is noticed that the graininess for every curve goes through
a maximum in accordance with subjective observations and the
results obtained by van Kreveld; furthermore, that the graininess
of the panchromatic emulsion is, for all observed density values, con-
siderably higher than that of the fine grain emulsion, and that the
difference is the more remarkable the closer the densities lie to the
maximum of the graininess.**

The effect of the increased time of development (which has no ef-
fect upon the density as the film was already thoroughly developed at
8 minutes) is not noticeable for small densities but becomes very im-
portant with the approach to the density Dmax of maximun graini-
ness. Here changes up to 30 per cent of G are found for A ,B, and
even larger values for C,D.

The influence of the developing time can be expressed in the devel-
oping time factor Q = GNJGNl where the suffix 1 represents the stand-
ard, the suffix 2 the abnormal developing time. The variation of Q

* In view of the physical causes of graininess, which without doubt are analogous
to colloidal coagulation, one should not expect a pure probability function, as the
grouping of grains can not be a statistical one as soon as it is affected by internal
forces.

** At this point it may be noted that the measurements of G have to refer to
the true transparency of the emulsion, which is not identical with the measure-
ment obtained from a densitometer if the base of the film is colored or matted.
Simple consideration, however, shows that the G values obtained with the graini-
ness meter are independent of additional absorption in the base, as this is auto-
matically compensated by the adjustment of the illumination in the photometer.
It is thus necessary only to subtract the density of the base from the values of the
abscissa in the G(D) diagrams.

534

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

with the density is shown for both emulsions in Fig. 13. It seems
that the curves have a definite maximum in the region of Dmax which
is definite for Fig. 13(a) and which has been drawn in Fig. 13(6) ten-

I3A.

05 1.0 Q J.5 2.0

015

FIG. 13. ( Upper} The graininess-density diagram of a
sensitive panchromatic emulsion developed 12 minutes
(.4), 8 minutes (B). The Q curve represents the change
of developing time factor with density.

(Lower) The graininess-density diagram of an extremely
fine grain emulsion developed 12 minutes (C), 8 minutes
(D). The dashed part of the Q curve is extrapolated.

tatively because sufficient G values for higher densities were not
available at the time. It must be noted that the Q values so far
represented are of provisional character, and have to be supported

Nov., 1937]

DETERMINATION OF GRAININESS

535

before a quantitative reality can be ascribed to them, although there
is little doubt that they represent the facts qualitatively. The ob-
vious conclusion to be drawn from these relations is that the graini-
ness is considerably increased by underexposure and overdevelop-
ment, particularly for regions in the neighborhood of Dmax.

(c) The Graininess Relation between Negative and Print. — The
graininess measurements have been applied to the quantitative de-
termination of the change of graininess that occurs when a negative

I4A

I4B.

O.I5

D

FIG. 14. Grain Jiess-density curves of different emulsions. The subscript
P denotes the positive taken from the negative with the subscript N.

is printed upon positive film by direct contact under normal printing
conditions.

In Fig. 14(a-d) the G(D) curves of Fig. 13 have been plotted sepa-
rately, and each of these curves has been combined with the G(D)
curve of a corresponding positive print made upon standard positive
film by means of a printing machine for a standard 7 = 2.1. The
density values in this diagram refer to the actual values of the emul-
sions, i. e., no account is taken of the relation between the negative
and the print made from it.

It is seen from the diagrams that in all cases the print is more

536

A. GOETZ AND W. O. GOULD

[J. S. M. P. E.

grainy than the negative, and much more so if the negative has a large
value of G. In order to clarify the particular relation between the
G value of the negative and its reproduction in the print, a "printing"
factor P has been evaluated as follows :

The values of GN of a negative and of the print made from it, GPI
are compared (in contrast to the previous comparison where the
G values of negatives and positives of equal density were compared)
by defining the ratio GP/GN =P. The printing factor P thus com-
pares the graininess of a dense negative with the graininess of a light
print and vice versa for different negatives, and the same positive

3.0

FIG. 15. The printing factor P plotted against the
density of the positive. A to D denote the negative
emulsions from which the prints were taken.

film. In Fig. 15 the P values obtained from Fig. 14 are plotted
against the density of the positive. For P = 1, both graininesses are
alike ; for P < 1, the graininess of the positive is smaller than the graini-
ness of the negative, and vice versa.

Fig. 15 demonstrates that for the same positive film the printing
factor is almost (probably within the limits of experimental error)
the same for different GN values. In other words, the graininess of a
print is directly proportional to the graininess of a negative for a given
density of the print. P is, however, variable with the density of the
print, in the sense that it increases with increasing density. For den-
sities below 0.4, GP is smaller than GN; whereas for higher density
values it increases rather rapidly; and around D = 2, P = 2.6,

Nov., 1937] DETERMINATION OF GRAININESS 537

which means that the graininess of a print of the density 2.0 is 2.6
times larger than the graininess of the negative from which the print
was taken. This means, for practical purposes that the relative in-
crease of the graininess by printing is large for the light regions of a
negative and small for the dark regions of the negative.

The fair coincidence of the observed values taken from entirely
different records appears to be a measure for the reliability of the
indications of the graininess meter.

It is likely that the steepness of the P(D) curve is different for
different printing materials and printing processes, in which case the
printing factor P could be used with advantage for the description of
the qualities of positive material.

In conclusion, the authors wish to express their gratitude for the
cooperation of the Agfa Ansco Corporation, Binghamton, at whose
instigation the work was undertaken, particularly to Drs. L. Eckler
and H. Meyer. They also wish to express their indebtedness to Dr.
A. Dember for his constructive criticism and contribution of many
valuable theoretical suggestions; and to Mr. C. H. Edler for his un-
tiring technical assistance. This work is part of the research pro-
gram of this laboratory supported by the Agfa Ansco Research Fund.

REFERENCES

1 VAN KREVELD, A. : "Graininess and Resolving Power of Photographic Emul-
sions," Phot. J., 74 (1934), p. 590.

1 VAN KREVELD, A.: "Objective Measurements of Graininess of Photographic
Materials," /. Opt. Soc. Amer., 26 (1936), p. 170.

3 ORNSTEIN, L. S., AND VAN KREVELD, A. : "The Reproduction of Photographic
Graininess by the Galvanometer of an Instrument for Density Measurement,"
Physica (III), 8 (19136), p. 815.

DISCUSSION

MR. ALBERSHEIM: In what way does the definition of the graininess depend
upon the resolving power of the photometer?

MR. GOETZ : The resolving power of the photometer and its influence upon the
values of G obtained by it have to be divided into three different components:
first, the optical resolving power of the microscopic system. It is easily seen that
there exists a lower limit for the resolving power beyond which the photometer
records becomes dependent upon it. The limit is characterized by the equality of
the resolving power of the system with the size of the smallest constituent (size
of the individual grain) of the transparency fluctuations of the emulsion under
investigation. Practically, this condition (that is, the sufficiency of the resolving
power) is satisfied by any well corrected optical system of a numerical aperture
larger than 0.65.

538 A. GOETZ AND W. O. GOULD

Second, the sensitivity of the photoelectric recording system: provided that
the recording system is aperiodic and has a frequency sufficiently far above the
highest frequency of recorded fluctuation, only the accuracy of determination of
G is affected, as the x scale on the integrator is always chosen to match the sensi-
tivity of the electric system.

Third, the size of the area a over which the photometer integrates at each in-
stant has a certain influence upon the determination of G that is difficult to define
mathematically. Closer consideration shows that the dependence of the ampli-
tude of the recorded fluctuation for a grain complex of given size and opaqueness
upon the size of a is represented by a hyperbolic function; that means that the
dependence of the amplitudes of fluctuations caused by a practically infinitely
large variety of sizes and shapes of such clusters results in a function resulting
from a superposition of an infinitely large number of hyperbolas with an infinite
variety of parameters. Whether or not such a function can be used for the theo-
retical evaluation of the dependence upon a is not easily decided, due to the fact
that the number is not quite infinite and the upper limit not exactly known. It
is therefore necessary to determine the dependence experimentally, which will be
done in the near future. For practical purposes we thus thought it necessary to
refer G to a certain size of a called the "standard-integer."

MR. TOWNSLEY: Have you investigated the influence the superposition of a
"uniform density" upon a "grainy density" has upon the quantitative determina-
tion of the graininess constant?

MR. GOETZ: Theoretically speaking, there should not be any influence of addi-
tional opaque levels without fluctuations upon the quantitative determination of
G. This problem is of immediate practical importance when measuring emulsions
with colored or opaque bases. Due to the fact that the illuminating light-source
of the photometer has always to be adjusted so that the sum total of transmitted
light entering the photometer is constant, any additional homogeneous opaqueness
has already been accounted for in the act of adjusting the light-source. If the
additional opaqueness is not perfectly homogeneous, as is practically always
the case, due to accidental lesions of the gelatin coating or due to dust,
etc., it also does not affect the determination of G, as such disturbances are ex-
tremely unlikely to follow a definite distribution function. Thus they eliminate
themselves, and the only effect of their presence is a slight additional indeter-
minacy of the value of G and not a change in the magnitude of G. It seems to us
that this particular quality of our method of graininess determination establishes
the principal difference from the determination of G by the measurement of an
"average deviation" or by the "photographic resolving power."

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus are held, in which various manufacturers of equipment describe and demonstrate
their new products and developments. Some of this equipment is described in the
following pages; the remainder will be published in subsequent issues of the Journal.

A SOUND KODASCOPE*

E. C. FRITTS AND O. SANDVIK**

The reproduction of sound on 16-mm. film employs the same general principles
as those used in sound reproduction on 35-mm. film, but owing to the nature of
the problems involved and the difference in the operating conditions encountered,
it is much more difficult to reproduce sound of satisfactory quality on 16-mm.
film: (1) The 16-mm. projectors are generally operated without enclosure, in the
same room as the audience. The noise of the projector, which has continually
been a problem in silent projection, becomes of paramount importance, since a
much lower level of noise than that found in old projectors is annoying with sound
accompaniment and materially interferes with the enjoyment and intelligibility
of the sound. (2) Sixteen-mm. projectors are generally operated by inexperi-
enced persons, and for this reason must be designed to provide the easiest and
most positive operation with all the controls easily accessible and to provide the
greatest insurance against film damage. In this connection, major considera-
tions are the operations that involve handling the film, such as threading and re-
winding. (5) The projector and its associated equipment are not permanently
installed, and it is necessary that both the size and the weight of the units be such
that they can be moved about. It is also necessary that they be protected by ade-
quate cases.

One of the most difficult problems, so far as the sound is concerned, is to assure
sufficiently uniform speed of the film through the scanning beam. The main
element in practically every device for this purpose is a flywheel of adequate ro-
tational inertia, which means considerable size and mass. The size and weight
considerations mentioned above present a difficult problem in the design of a me-
chanical filter that will work with a smaller flywheel. An added complication in a
16-mm'. sound projector is the provision for the projection of silent films, which
are taken at 16 instead of 24 frames per second. This provision requires a pull-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received
June 22, 1937. Communication No. 628 from the Kodak Research Laboratories.
** Eastman Kodak Co., Rochester, N. Y.

539

540

NEW MOTION PICTURE APPARATUS

[J. S. M. P. E.

down movement to operate within a sufficiently limited angle to provide the
necessary three interruptions of light per frame to overcome flicker at the silent

FIG. 1. Carrying cases for loud speaker and projector.

speed, and, at the same time, to be sufficiently quiet when operated at 24 frames

per second.

Such are the problems involved, and the Sound Kodascope has been designed

as the best possible compromise be-
tween these various limitations and
with the cost of the machine only a
secondary consideration.

Two carrying cases are provided for
the projector and the associated equip-
ment (Fig. 1). One of these accom-
modates the projector, the power cord,
and a 400-ft. reel. The second, which
serves as the loud speaker cabinet, is
also provided with storage space for
the cable connecting the pre-amplifier
on the projector, with the power ampli-
fier in the speaker cabinet, a 1600-ft.
reel, extra lenses, and some minor
parts.

The projector unpacked from the
case is shown in Fig. 2. When not in

_, 0 _ . ., use, it is completely enclosed by a

FIG. 2. Projector as it appears . ' . *

unpacked from the carrying case. satin-finished aluminum case which

forms an integral part of the machine.

The front portion of the projector case opens in two parts on two hinges, thus
completely disclosing the threading mechanism as shown in Fig. 3. The reel

Nov., 1937]

NEW MOTION PICTURE APPARATUS

541

arms unfold from the body of the projector into positions allowing ample
clearance for 1600-ft. reels as shown in Fig. 4. The take-up reel operates
at right angles to the supply reel. This construction makes for compactness
in the operating area because the plane in which the take-up reel operates is
parallel and close to the front and face of the machine. By virtue of this ar-
rangement, the film is given a half twist and enters the take-up reel at a slight
angle, minimizing any possible scraping against the outer flanges of the reel.

FIG. 3. Front covers of projector swung aside, disclosing the
threading mechanism.

Threading the projector is very easy. Starting from the supply reel, the film
is led over the feed sprocket, down through the curved gate which has been thrown
forward by the starting and stopping lever. From the gate the film is passed
over a lower loop-forming roller, over the sound drum, thence it is pushed through
a slot onto the sound sprocket and through a channel to a pair of snubbing roll-
ers, from which it passes over a tapered guide roller and takes a right-angled
turn to the take-up reel. The loops are formed automatically by two rollers, one

542

NEW MOTION PICTURE APPARATUS

[J. S. M. P. E.

10

6

.
61

Nov., 1937] NEW MOTION PICTURE APPARATUS 543

above and one below the picture gate, which move out while the starting lever
travels forward in a clockwise direction. When the loops have been formed to
exact size, the gate moves into place, the loop-forming rollers return to their
initial position, and, as the starting lever approaches its extreme clockwise posi-
tion, it closes the motor switch. If one desires to check the threading, a push-
button has been provided which momentarily closes the motor circuit. This
can be done either before or after the gate has been closed and provides a con-
venient and positive check on the threading before the main switch is closed.

Aside from ease of operation, this method of threading has the additional ad-
vantage that, since the loops are always formed to exactly the same size, syn-
chronism is assured. When the threading has been completed, a section of the
case may be closed, thus enclosing the loops and materially reducing the noise.
The section of the cover in its closed position does not interfere with the various
controls required for operation.

The projector is supplied with an //1 .6 lens of 2-inch focus; but the lens mount
is designed for the interchange of lenses by means of a convenient cam latching
device and will accommodate an //1. 6 lens of 4-inch focus. The entire front of the
gate assembly may be removed for cleaning and inspection. The front part of
the gate also includes a framing device. A 750-watt projection lamp is standard
equipment, but other lamps may be used. By moving the knob on the front of
the machine between two positions, the projector may be run at the constant speed
of 18 frames per second for silent film or 24 frames per second for sound-film.

The rewind mechanism, which is operated by a second motor, is located in the
top of the projector. This mechanism engages with the supply reel by turning
the latter through an angle of 90 degrees, as shown in Fig. 5.

The pull-down mechanism is the result of an extended investigation which in-
cluded a great many types of pull-downs. Its mechanism is on the lamp side of
the film, leaving the body of the projector on the other side of the film free from
other elements, such as the sound mechanism. The pull-down is essentially a
symmetrical Lumiere cam movement. The claw (Fig. 6) is integral with the
cam shoes and is cut from a solid piece of steel so that the mass may be a mini-
mum. The two cams operating the claw are carried on the same shaft which is
accelerated by an off-center drive Instead of the customary hit-and-miss action,
so that the pull-down movement is covered by a shutter equivalent to 60 degrees
of the pull-down cycle.

To reduce the noise arising from acceleration of the cam shaft, the mass is
minimized by cutting it from a solid bar of steel except for the in-and-out cam.
The dimensions of the in-and-out cam provide just the necessary withdrawal of
the claw from the film on the return stroke, and the surface on which it bears is
shaped to cause the claw to follow a prescribed path during the pull-down stroke.
The whole movement operates in a dust-tight enclosure and is constantly flooded
with oil. In the design of the pull-down, serious consideration has been given
to the elimination of unsteadiness in projection. To this end, bending stresses
have practically been eliminated from the claw and the acceleration at the end
of the pull-down stroke is very low, requiring a low tension or friction in the gate.
It will be noted that only a single claw engages the film. Some projectors use
two claws in tandem on the same side of the film. A tandem claw does permit
the pull-down movement to pass a section of film in which there is a single dam-

544

NEW MOTION PICTURE APPARATUS

[J. S. M. p. E.

1

E

Nov., 1937]

NEW MOTION PICTURE APPARATUS

545

aged perforation without loss of loop. However, if two successive perforations
are damaged, the loop will be lost. It has been claimed that a tandem claw dis-
tributes pressure on the film, reduces the wear, and increases the life of the film.
Experience has shown that the life of film is determined not by the number of
times it passes through the projector, but by accidental damage in handling it.

The seriousness of losing a loop is the resulting damage to the film and the diffi-
culty of rethreading. The Sound Kodascope film-handling mechanism is so de-
signed that it is practically impossible to damage film by loss of loop. Further-
more, the loop may be reestablished most easily by turning the operating knob
off and returning it to the operating position.

As stated earlier, the film motion through the scanning beam is generally gov-
erned by some type of mechanical filter whose main element is a flywheel. The
function of this filter is to isolate the film from various disturbances that would
otherwise act upon it. After studying several such devices, the one shown in

IOOO
FREQUENCY

10,OOO

FIG. 8. Overall frequency characteristic from film to acoustic pressure,
film loss not included.

Fig. 7 was chosen as being the most practicable at the present time. The sound-
track is scanned on film drum 1, whose motion governs that of the film at this
point. This film drum is mounted rigidly on a shaft which also carries a flywheel
2 and a second drum 3. This system is driven by a viscous coupling between the
drum 3 and a hollow shel| 4, which, in turn, is driven by the projector mechanism.
The mechanical filter as a whole is designed so that the viscous medium is pro-
vided from the same oil bath as that used for lubricating and silencing the pro-
jector mechanism.

Under ideal or specified conditions of operation, the performance of this drive
approaches perfection. While the change of viscosity of the oil with tempera-
ture, and the change of perforation pitch with film shrinkage, in extreme cases,
would interfere with the performance of the filter, these extreme cases are not
normally encountered in practice.

As stated previously, the power amplifier is mounted in the loud speaker cabi-
net ; while the pre-amplifier is mounted at the bottom of the front side of the pro-
jector and can readily be detached for servicing. The photoelectric cell is re-

546

NEW MOTION PICTURE APPARATUS

[J. S. M. P. E.

moved with the pre-amplifier. On the front face of the pre-amplifier housing is
the volume control knob; this knob also actuates the off-and-on switch. Below
this knob is a microphone jack, by which a microphone can be connected to the
amplifier. Immediately above the knob is a tone-control switch, whose purpose
is partially to compensate for variation in the frequency characteristics and other
qualities of 16-mm. prints.

Owing to the variations in print quality, the choice of the overall frequency

FIG. 9. Protective cover removed from the sound
optical system showing the exciter lamp and the lens
tube with its mount.

characteristic of the sound reproducing system is difficult and depends largely
upon guesswork.

In designing the reproducing system, the aim was to obtain a frequency char-
acteristic essentially uniform between 150 and 6500 cps., exclusive of the film
loss. This choice was made upon the basis that a sufficient number of good prints
are available to justify this frequency range. The actual acoustic output ob-
tained from a print previously corrected for film loss, on a projector picked at
random, is shown in Fig. 8. The slight rise in the curve in the region between
170 and 600 cps. is due to cavity resonance in the loud speaker cabinet.

Nov., 1937] NEW MOTION PICTURE APPARATUS 547

There are a large number of prints which, from poor definition, excessive ground-
noise, and other causes, will sound better and be more intelligible when the fre-
quency range of the amplifier is reduced, and hence a tone control has been pro-
vided which reduces the amplification of both the high and the low frequencies.
Prints can be made on existing commercial equipment and material that would
justify considerable extension of the frequency range.

The sound optical system and the exciter lamp are shown in Fig. 9, with the
protective cover removed. The exciter lamp, which is rated at 0.75 ampere, 4
volts, is equipped with an automobile headlight type prefocus base. Since the
type of optical system used is not critical to lamp filament position, this method
of locating it is quite satisfactory. The optical system is carefully adjusted at
the factory and should require no further attention. A knob at the front end of
the projector is provided for shifting the focus of the sound optical system from
one side of the film to the other. This adjustment is necessitated by the fact that
original black-and-white reversal prints, and, generally, reduction prints from
35-mm. film, must run through the picture gate with the emulsion side of the film
toward the projection lens ; duplicate contact prints from original black-and-white
reversal positives and some types of original reversal color positives must be run
with the emulsion side away from the projection lens. Thus, if the focus of the
optical system can not be shifted from one side of the film to the other according
to the emulsion position, a serious loss results in the high frequencies, amounting
to as much as 15 db. at 4000 cps. for a large-aperture optical system.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D. C.t
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

British Journal of Photography

84 (Aug. 13, 1937), No. 4032

The Elimination of the Reseau Pattern from Color
Separation Negatives from Dufaycolor Transparen-
cies (p. 513). F. J. TRITTON

Electronics

10 (Aug., 1937), No. 8

Video Amplifier Design (p. 22). R. L. FREEMAN AND

J. D. SCHANTZ

International Projectionist

12 (Aug., 1937), No. 8

The Neon Tube Oscilloscope as a Precision Servicing

Instrument, II (p. 10). T. P. HOVER

Typical Troubles in Modern Sound Reproducing Units,
III (p. 14). L. CHADBOURNE

Projector Mechanism Tolerances and Inter-tolerances

(p. 15). H. GRIFFIN

Argon vs. Mercury Vapor Tubes for Projection Recti-
fiers (p. 17). J. K. ELDERKIN

Fundamentals of Sound Recording and Theater Repro-
duction (p. 20). F. T. JAMEY, JR.

Journal of the Optical Society of America

27 (Aug., 1937). No. 8
Note on Illumination Characteristics of the Camera

Lens (p. 286). F. BENFORD

Projective Transformations of I. C. I. Color Specifica-
tions (p. 294). D. L. MACADAM
A Comparative Study of Some Violet-Absorbing Filters

(p. 303). P.L.BAYLBY

548

CURRENT LITERATURE

549

Motion Picture Herald (Better Theaters Section)

128 (Aug. 21, 1937), No. 8
The Use of Existing Parts with New Sound Equipment

(p. 31). A. NADELL

Theater Acoustics Today (4. Frequency Analyses:

Treatment Distribution) (p. 36). C. C. POTWIN

Photographic Journal

77 (Aug., 1937), No. 8

Photographic Development and the Latent Image
(p. 497).

Proceedings of the Institute of Radio Engineers

25 (Aug., 1937), No. 8
Development of the Projection Kinescope (p. 937).

High-Current Electron Gun for Projection Kinescopes

(p. 954).
Theoretical Limitations of Cathode-Ray Tubes

(p. 977).

A Circuit for Studying Kinescope Resolution (p. 992).
An Oscillograph for Television Development (p. 1012).
The Brightness of Outdoor Scenes and Its Relation to

Television Transmission (p. 1034).

Television Pick-up Tubes with Cathode-Ray Beam

Scanning (p. 1048)
Theory and Performance of the Iconoscope (p. 1071).

R. M. EVANS
W. T. HANSON

V. K. ZWORYKIN AND

W. H. PAINTER
R. R. LAW

D. B. LANGMUIR
C. E. BURNETT
A. C. STOCKER

H. IAMS, R. B. JANES,
AND W. H. HICKOK

H. IAMS AND A. ROSE
V. K. ZWORYKIN,
G. A. MORTON, AND
L. E. FLORY

Technical Bulletin — Academy of Motion Picture Arts and
Sciences

(August 10, 1937)
Standard Nomenclature for Filters

La Technique Cinematographique

9 (July, 1937), No. 79

L'Emulsion Cinematographique et son Emploi (Mo-
tion Picture Emulsion and Its Application) (p. 967). A. P. RICHARD

HIGHLIGHTS OF THE FALL CONVENTION

HOTEL PENNSYLVANIA, NEW YORK, N. Y.
OCTOBER 11-14, 1937

Despite the fact that the summer, a season of more or less restricted activity
due to vacations and other causes, intervened, the technical quality of the papers
at this Convention was of a high standard, and, judging from the extensive dis-
cussions following many of the presentations, the choice of papers was of con-
siderable interest to those attending the convention. Of particular note is the
fact that this Convention included presentations and demonstrations of the three
most promising and more or less immediate future developments of outstanding
importance to the industry — namely, stereophony, stereoscopy, and television.
The subject of color motion pictures was not included in the program, beyond the
presentation of a few outstanding examples of 16-mtn. Kodachrome, incidental
to the demonstration of a new scheme for enhancing the beauty of the projected
screen image by means of a specially constructed reflecting surface about the
periphery of the screen.

TECHNICAL SESSIONS

The Convention opened at 10 A.M. on Monday, October llth, with a few
remarks by President Wolf, several committee reports, a demonstration and pa-
per from Cornell University on the recording of bird calls, an interesting paper
dealing with foreign film markets by N. D. Golden, and a discussion of technologic
applications of motion pictures in designing telephone apparatus.

At noon of the same day the usual informal get-together luncheon was held, at-
tended by approximately 150 members and guests. After a few words of welcome
by the President, the results of the fall elections were announced as follows:

Executive Vice-President: K. F. MORGAN
Engineering Vice-President: L. A. JONES
Financial Vice-President: E. A. WILLIFORD
Secretary: J. FKANK, JR.
Treasurer: L. W. DAVEE
Governors: R. E. FARNHAM

H. GRIFFIN

A. C. HARDY

Interesting addresses were made by Mr. Martin Quigley on the subject of
"Propaganda, Education, and the Entertainment Film," and by Mr. Louis
Nizer, Secretary of the New York Film Board of Trade.

The highlight of the Monday afternoon program was the demonstration of
stereoscopic motion pictures by G. W. Wheelwright, based upon the use of polar-
oid, a polarizing material described previously in the JOURNAL. The stereoscopic
effect was demonstrated with 16-mm. Kodachrome pictures.
550

FALL CONVENTION 551

During the afternoon the Active and Fellow members were requested to vote
upon the recommendation of the Board of Governors that the distinguished Brit-
ish pioneer and scientist, Robert William Paul, be elected to Honorary Member-
ship. Mr. Paul had been previously unanimously recommended for this honor
by the Historical and Honorary Membership Committees. A citation was read
by Mr. G. E. Matthews of the Historical Committee and Mr. Paul was unani-
mously elected.

The Monday evening session of the Convention was held in the auditorium of
the Bell Telephone Laboratories and was devoted to developments in both disk
and film recording and reproduction. Papers were read on the subjects of disk
recording (by M. J. Di Toro, and L. Vieth and C. F. Wiebusch), 96-cycle fre-
quency modulation of sound-film records (by J. Crabtree and W. Herriott), and
a description and proposed nomenclature for various types of sound-track of
movietone releases (by J. K. Hilliard). A demonstration of stereophonic record-
ing and reproduction was given by the Electrical Research Products, Inc., pat-
terned after the arrangement demonstrated by H. Fletcher several years ago.
A special motion picture has been made and recorded with twin sound-tracks,
which were reproduced through separate channels by speakers located at each
side of the screen. The directional effect was perhaps not as apparent as might
have been desired but was decidedly noticeable in orchestral numbers. Further
work will be necessary to determine the best locations of the microphones and
speakers. Mr. Maxfield, who supervised the demonstration, made the interesting
statement that he preferred the sound quality from a twin system flat to 5000
cps. to that from a single-system flat to 15,000 cps. So far as is known, this was
the first public demonstration of stereophonic sound in conjunction with motion
pictures.

The morning of Tuesday, October 12th, was devoted to engineering practice,
and included an assortment of papers on the subjects of air-conditioning and the
use of various materials such as stainless steel, Inconel, and die castings in mo-
tion picture equipment. In addition, a paper discussing the design and operation
of vacuum tubes for use in motion picture processes was presented by L. C. Hol-
lands and A. M. Glover.

Light and illumination was the keynote of the Tuesday afternoon session.
F. T. Bowditch and A. C. Downes discussed the characteristics of carbon arcs,
and a paper by S. Dushman, Assistant Director of Research of the General Electric
Co., dealt with recent developments in gaseous discharge lamps. G. G. Popovici
described some developments in background projection, and the subject of light
control in photography by G. Mili concluded the afternoon.

Perhaps the outstanding presentation of the afternoon was the paper by B.
Schlanger entitled "A Method of Enlarging the Visual Field of the Motion Pic-
ture Screen." By utilizing a screen with semi-transparent boarders, the trans-
mitted light was reflected and scattered by rear reflecting surfaces so as to pro-
duce in effect a vignette around the screen. As the brilliancy of the screen image
would change, or, in the case of Kodachrome, as the color would change, so would
the brightness or hue of the screen extension change. The sharp unnatural black
screen edge is avoided, and the effect that was produced could probably be aptly
described as "luminous vignetting."

The entire morning of Wednesday, October 13th, was devoted to practical

552 FALL CONVENTION [J. s. M. p. E.

projection, including the Report of the Projection Practice Committee. The
latter dealt principally with the change of projector aperture dimensions recently
proposed by the Academy of Motion Picture Arts and Sciences. A symposium
of several papers, arranged with the cooperation of Mr. F. H. Richardson, dealt
with various problems encountered in projection, and the morning closed with an
open forum on related subjects.

The afternoon of Wednesday, October 13th, was left open, although arrange-
ments were made for those members who so wished to inspect the projection
facilities of the Radio City Music Hall, through the courtesy of Mr. Harry Braun.
On Wednesday evening was held the Semi-Annual Banquet and Dance of the
Society. Opening the proceedings of the Banquet were a few words of welcome
by the President, who then introduced the officers-elect and several distinguished
guests.

Mr. A. Demaria, representing the French Association of Cinematographers,
proposed a toast to the success of our Society, and Mr. Francis Doublier referred
briefly to some of his work with Lumiere in the early davs of the motion picture
in France from 1894 to 1901. Mr. H. G. Govil, representative of the Motion
Picture Society of India, spoke briefly of some of the motion picture problems in
India. Following these addresses, Mr. C. C. Pettijohn, General Counsel of the
Motion Picture Producers and Distributors of America, Inc., the principal
speaker of the evening, discussed at considerable length the relations between the
engineers of the industry and the fruits that they derive from their labors and
activities.

A citation of the work of Dr. Dean Brewster Judd, who was selected as the
recipient of the 1936 Journal Award, was next read by Mr. E. A. Williford, Chair-
man of the Journal Award Committee. The Award was made to Dr. Judd in
recognition of his paper on "Anomalies of Vision and Color Blindness."

Honorable mention was made by Mr. Williford of two additional papers selected
from the 1936 publications in the JOURNAL, viz., "Improved Resolution in Sound
Recording and Printing by Use of Ultraviolet Light," by G. L. Dimmick, and
"Continuous Photographic Processing" by H. G. Hineline.

The recipient of the Progress Medal for 1937 was Edward Washburn Kellogg,
of RCA Manufacturing Company, a citation of whose work was read by Mr.
E. W. Engstrom. The granting of the Award by President Wolf was followed
by an address of acknowledgment and appreciation by Mr. Kellogg.
The evening was concluded with entertainment and dancing.
The morning session of Thursday, October 14th, was devoted to motion pic-
ture apparatus. Papers were presented describing sound-level meters, motion
picture camera cranes, and miscellaneous equipment for motion picture projec-
tion. The afternoon of Thursday was devoted to sound and photography, as
listed in the final program. Kellogg's discussion of loop-length variation in non-
slip printers and Maxfield's account of sound pick-up for stereophonic recording
aroused considerable interest at the session.

An outstanding climax to the Convention was the television demonstration
arranged by the Radio Corporation of America through the courtesy of Mr.
Ralph Beal, Director of Research of RCA. The demonstration was held on the
62nd floor of the RCA Building, New York. Twenty television receivers, each
viewed by a group of ten or fifteen persons, picked up signals transmitted from

Nov., 1937] FALL CONVENTION 553

the Empire State Building. The program originated in an NBC Studio on the
third floor of the RCA Building, whence it was transmitted via coaxial cable to
the transmitter in the Empire State Building and thence radiated back to the
RCA Building. The program consisted of comedy and vaudeville sketches by
live artists and the transmission of a motion picture film newsreel.

The proceedings of the evening were opened with a brief address by Mr.
David Sarnoff, President of the Radio Corporation of America, who was intro-
duced by Mr. J. I. Crabtree, Editorial Vice-President of the Society.

Two performances were given, in order to accommodate the 400 or more per-
sons who attended. At the end of each performance an informal interview be-
tween one of the studio performers and a member of the Society was televised and
transmitted. Mr. L. W. Davee, Treasurer of the Society, participated in the first
interview, and Mr. E. A. Williford, Financial Vice-President elect, in the second.
The picture size was approximately 7 by 9 inches and the image was of astonish-
ingly good quality and neutral in color. The definition was such that in the case
of the newsreel football game the path of the ball was easily followed. In an
adjoining room a film 3 by 4 feet was projected upon a screen from a new high-
intensity Iconoscope, this being the first public demonstration of this new de-
velopment.

At the conclusion of the demonstration Mr. Crabtree expressed appreciation of
the Society to the research workers at Camden, and to Mr. Sarnoff and the mem-
bers of the staff of RCA for the great privilege extended to the Society. He also
reminded the members that they had seen motion pictures printed and projected
by electrooptical means without the medium of film, and that it was apparent that
from now on the Society must pay increasing attention to the important subject
of television.

The Convention adjourned at 11 P.M., Thursday, October 14th.

ACKNOWLEDGMENTS

Conventions of the Society are made possible only through the cooperation and
collaboration of a large number of Officers, members, friends, and companies.
The general facilities of the Convention were arranged by Mr. W. C. Kunzmann,
Convention Vice-President; Mr. H. Griffin and Mr. J. Frank, Jr., in charge of
projection facilities; Mr. G. Friedl, Jr., Chairman, Local Arrangements Commit-
tee; Mr. A. S. Dickinson, Chairman, the Banquet Committee; Mrs. S. K. Wolf
and Mrs. O. F. Neu, Hostesses; Mr. W. Whitmore, Chairman, Publicity Commit-
tee; and Mr. E. R. Geib, Chairman, Membership Committee.

Credit for the Papers program and technical arrangements are due to Mr. J. I.
Crabtree, Editorial Vice-President, and Mr. G. E. Matthews, Chairman, Papers
Committee. Much assistance was rendered in preparing the program by members
of the Society on both the East and West coasts.

Thanks are due also to the officers and members of Local 306 I. A. T. S. E.
for providing the projectionist for the Convention.

Among the companies who contributed in equipment and service to the Con-
vention were the following: International Projector Corp., National Carbon Co.,
Raven Screen Co., Eastman Kodak Co., Harry A. Strong Co., Bausch & Lomb
Optical Co., Electro-Acoustic Products Co., Electrical Research Products, Inc.,

554 FALL CONVENTION

J. E. McAuley Manufacturing Co., National Theatre Supply Co., and Motion
Picture Lighting and Equipment Co.

The Society is indebted to the following companies for the films loaned for the
motion picture performance held on the evening of Tuesday, October 12th:
Universal Pictures Corp., United Artists, March of Time, RKO Radio Pic-
tures, Fox Movietone, Fleischer Pictures, and The Museum of Modern Art Film
Library.

Acknowledgment is due also to Radio City Music Hall, Paramount Theatre,
Roxy Theatre, and Warner Strand Theatre for supplying passes to members and
guests during the week of the Convention; and to Warner Brothers and Para-
mount for providing entertainment features for the Banquet.

The Radio Corporation of America and the National Broadcasting Company
are to be thanked for arranging the television demonstration on Thursday evening,
and the Radio City Music Hall for arranging an inspection tour of the technical
facilities.

Thanks are due to Bell Telephone Laboratories for holding the Monday even-
ing session in the auditorium of the Laboratories building.

PROGRAM

FALL, 1937, CONVENTION, NEW YORK, N. Y.
HOTEL PENNSYLVANIA

MONDAY, OCTOBER llth

10:00 a. m. Business and General Session.

Opening Remarks by President S. K. Wolf.

Report of the Convention Committee; W. C. Kunzmann, Conven-
tion Vice-President.

Report of the Membership Committee; E. R. Geib, Chairman.

Society Business; Election of Officers and Other Business.

"Hunting the Songs of Vanishing Birds with a Microphone;"
P. Kellogg, Laboratory of Ornithology, Cornell University,
Ithaca, N. Y. (Demonstration.)

"Safeguarding and Developing Our Film Markets Abroad;" N. D.
Golden, Motion Picture Division, U. S. Department of Commerce,
Washington, D. C.

"High-Speed Motion Picture Photography Applied to the Design
of Telephone Apparatus;" W. Herriott, Bell Telephone Labora-
tories, Inc., New York, N. Y. (Demonstration.)

12:30 p. m. Informal Luncheon.

For members, their families, and friends.

Address by Mr. Martin Quigley, President, Quigley Publishing Co.,

Inc., New York, N. Y.: "Propaganda, Education, and the

Entertainment Film."
Address by Mr. Louis Nizer, Secretary, New York Film Board of

Trade, New York, N. Y.

2:00 p. m. Photographic and Laboratory Session.

"Further Progress in Film Storage;" J. G. Bradley, National
Archives, Washington, D. C.

"The Effect of the Composition of an MQ Developer on Its Reduc-
tion Potential;" R. M. Evans and W. T. Hanson, Jr., Kodak
Research Laboratories, Rochester, N. Y.

"A Modern Motion Picture Laboratory;" C. L. Lootens, Republic
Productions, Inc., North Hollywood, Calif.

"Modulated High-Frequency Recording as a Means of Determining
Conditions for Optimal Processing;" J. O. Baker and D. H.
Robinson, RCA Manufacturing Co., Inc., Camden, N. J.

* As actually followed at the meetings. All sessions were held in the Salle
Moderne of the Hotel unless otherwise noted.

555

556

FALL CONVENTION

[J. S. M. p. E.

"Possibilities of Stereoscopic Motion Pictures;" G. W. Wheel-
wright, 3d, Land-Wheelwright Laboratories, Boston, Mass.
( Demonstration .)

8:00 p. m. Auditorium, Bell Telephone Laboratories; Special Sound Session.
"Distortion in the Reproduction of Hill-and-Dale Records;" M. J.

Di Toro, Thomas A. Edison, Inc., Orange, N. J.
"Suggested Standard Nomenclature for Release Print Sound -

Tracks;" J. K. Milliard, Metro-Goldwyn-Mayer Studios, Culver

City, Calif. (Demonstration.)
"Film Perforation and 96-Cycle Frequency Modulation in Sound-

Film Records;" J. Crabtree and W. Herriott, Bell Telephone

Laboratories, Inc., New York, N. Y.
"Recent Developments in Hill-and-Dale Recorders;" L. Vieth

and C. F. Wiebusch, Bell Telephone Laboratories, Inc., New

York, N. Y. (Demonstration.)
"Stereophonic Recording and Reproduction from Motion Picture

Film Records;" Introductory Remarks by J. P. Maxfield,

Electrical Research Products, Inc., New York, N. Y. (Demon-
stration.)

TUESDAY, OCTOBER 12th

10:00 a. m. Engineering Practice Session.

"Air-Conditioning with Lithium Chloride;" G. A. Kelley, Surface

Combustion Corp., Toledo, Ohio.
"The Activated Alumina System as Applied to Air-Conditioning

and Drying Problems;" G. L. Simpson, Pittsburgh Lectrodryer

Corp., Pittsburgh, Pa.
"Die Castings and Their Application to Photographic Appliances;"

J. C. Fox, Doehler Die Casting Co., Toledo, Ohio.
Report of the Standards Committee, E. K. Carver, Chairman.
"The Use of Inconel for Photographic Film Processing Equipment;"

G. L. Cox, International Nickel Co., New York, N. Y^
"Newer Types of Stainless Steel and Their Applications to Photo-
graphic Processing Equipment;" H. A. Smith, Republic Steel

Corp., Massillon, Ohio.
"Vacuum-Tube Engineering for Motion Pictures;" L. C. Hollands

and A. M. Glover, RCA Manufacturing Co., Inc., Harrison, N. J.

2:00 p. m. Lighting and Studio Session.

"Spectral Distribution and Color-Temperature of the Radiant

Energy from Carbon Arcs Used in the Motion Picture Industry;"

F. T. Bowditch and A. C^ Downes, National Carbon Co., Inc.,

Cleveland, Ohio.
"Recent Developments in Background Projection;" G. G. Popovici,

J. G. Saltzman, Inc., New York, N. Y. (Demostrat.ion.)
"A Method of Enlarging the Visual Field of the Motion Picture

Screen;" B. Schlanger, New York, N. Y. (Demonstration.)

Nov., 1937] FALL CONVENTION 557

"Recent Developments in Gaseous Discharge Lamps;" S. Dush-
man, Research Laboratory, General Electric Co., Schenectady,
N. Y.

Report of the Studio Lighting Committee, R. E. Farnham, Chairman.

"Light Control in Photography;" G. Mili, Westinghouse Electric
& Manufacturing Co., Bloomfield, N. J.

8:00 p. m. Motion Pictures.

Showing of Selected Historical Sound Motion Pictures arranged by

Mr. John E. Abbott, Director, Film Library of the Museum of

Modern Art, New York, N. Y.
Showing of a Recent Feature Picture and Shorts.

WEDNESDAY, OCTOBER 13th

10:00 a. m. Projection Practice Session, A. N. Goldsmith, Chairman; J. D.
Basson, Vice-Chairman.

"The Practice of Projection;" A. N. Goldsmith, New York, N. Y.

"Grading Projectionists;" G. P. Barber, Government of the
Province of Alberta, Edmonton, Alberta, Canada.

"Cooperation as the Keynote of Successful Small Town Projec-
tion;" T. P. Hover, Warner's Ohio Theater, Lima, Ohio.

"A Discussion of Screen Image Dimensions;" F. H. Richardson,
Quigley Publishing Co., Inc., New York, N. Y.

Report of the Projection Practice Committee, H. Rubin, Chairman.

"Precision All-Metal Reflectors for Use with Projection Arcs;"
C. E. Shultz, Heyer-Shultz, Inc., New York, N. Y.

"Perforated Screens and Their Faults;" F. H. Richardson, Quigley
Publishing Co., Inc., New York, N. Y.

"Commercial 16-Mm. Projection Faults;" C. L. Greene, Minne-
apolis, Minn.

"Careless Work in Printing Sound-Tracks on Release Prints;"
I. Gordon, Norka Theater, Akron, Ohio.

Open Forum on Projection Problems.

2 :00 p. m. Open Afternoon.

7:30 p. m. Semi- Annual Banquet.

Address by Mr. Charles C. Pettijohn, General Counsel, Motion
Picture Producers and Distributors of America, New York, N. Y.
Introduction of Officers elect.
Presentation of SMPE Journal Award.
Presentation of SMPE Progress Medal.
Entertainment and Dancing.

THURSDAY, OCTOBER 14th

10:00 a. m. Apparatus Symposium and Manufacturers' Announcements.

"The Sound-Level Meter in the Motion Picture Industry;" H. H.
Scott and L. E. Packard, General Radio Co., Cambridge, Mass.

558 FALL CONVENTION

"A New Motion Picture Camera Crane;" E. H. Heyer and E. L.
Fischer, Universal Pictures Corp., Universal City, Calif.

"New Ideas in Mobile Sound Recording Equipment;" J. G.
Matthews and C. M. Ralph, General Service Studios, Inc.,
Hollywood, Calif.

"A Mobile Sound Recording Channel;" L. T. Goldsmith and
B. F. Ryan, Warner Brothers Pictures, Inc., Burbank, Calif.

"A Device for Cleaning the Sound-Track of Motion Picture Film
During Projection;" R. J. Fisher, Rochester, N. Y. (Demon-
stration.)

"A Flash Fire- Valve for Fire Prevention in Motion Picture Pro-
jectors;" R. J. Fisher, Rochester, N. Y.

"A Sound-Film Phonograph;" D. Canady and V. A. Welman,
Canady Sound Appliance Co., Cleveland, Ohio.

"Simplified Device for Cueing Motion Picture Films;" R. Vincent,
Reeves Sound Studios, Inc., New York, N. Y.

2:00 p.m. Sound and Photography Session.

"Reduction of Loop-Length Variations in Non-Slip Printers;"

E. W. Kellogg, RCA Manufacturing Co., Inc., Camden, N. J.
"A Recorder for Making Buzz-Tracks;" E. W. Kellogg, RCA

Manufacturing Co., Inc., Camden, N. J.
"Recording Tests on Some Recent High-Resolution Experimental

Emulsions;" J. O. Baker, RCA Manufacturing Co., Inc., Camden,

N.J.
"Sound Pick-Up Methods for Motion Pictures;" J. P. Maxfield,

A. W. Colledge, and R. T. Friebus, Electrical Research Products,

Inc., New York, N. Y.
"Grain-Size Determination and Other Applications of the Callier

Effect;" J. Eggert and A. Kuester, I. G. Farbenindustrie Film

Fabrik, Wolfen, Germany.

8:00 and

9:15 p. m. Television Demonstration.

Arranged by Radio Corporation of America, New York, N. Y.
On the 62nd floor of the RCA Building, 30 Rockefeller Plaza,
New York, N. Y. As the demonstration could be shown con-
veniently to only about 200 persons at a time, arrangements were
made for two showings.

ABSTRACTS OF PAPERS OF THE
FALL CONVENTION

AT

NEW YORK, N. Y.
OCTOBER 11-14, 1937

The Papers Committee presents the following abstracts of papers presented at the
recent Fall Convention in view of the fact that some of the papers may not be published
for several months. The papers presented at Conventions constitute the bulk of the
material published in the Journal, and so must be spread over the several months inter-
vening between Conventions.

PAPERS COMMITTEE

G. E. MATTHEWS, Chairman

C. N. BATSEL C. FLANNAGAN T. E. SHEA

L. N. BUSCH M. E. GILLETTE P. R. VON SCHROTT

O. O. CECCARINI E. W. KELLOGG H. C. SILENT

A. A. COOK R. F. MITCHELL H. G. TASKER

L. J. J. DIDIEE W. A. MUELLER I. D. WRATTEN

E. C. RICHARDSON

"Hunting the Songs of Vanishing Birds with a Microphone;" P. Kellogg,
Laboratory of Ornithology, Cornell University, Ithaca, N. Y.

A resume of the idea behind recording bird songs is presented, including a brief
discussion of the usefulness of bird song studies to students of Ornithology; pres-
ent methods of recording songs; and early attempts at phonographic recording.

The rise of interest in recording bird songs at Cornell is described. This in-
cludes the first recordings in cooperation with the Fox-Case Corporation and sub-
sequent work with A. R. Brand.

Problems in recording bird songs in the wild : the high frequencies of bird song ;
the necessity of working at relatively great distances from the subject; wind and
other noises ; the need for portability and simplicity of the equipment, all combine
to increase the difficulties of the work. The solution of these problems has been
partly accomplished, and methods are discussed, including the advantages and
faults of parabolic concentrators.

"Safeguarding and Developing Our Film Markets Abroad;" N. D. Golden,
Bureau of Foreign and Domestic Commerce, Department of Commerce, Washing-
ton, D. C.

American motion pictures are maintaining their immense popularity through-
out the world, yet the barriers and obstructions that tend to limit their sales
continue to be imposed abroad. Safeguarding and developing our film market
abroad, "contingents" taxes, and complex restrictions, which continue to be im-
posed in all too many instances are some of the problems American Producers

559

560 FALL CONVENTION [J. s. M. p. E.

must face abroad. Some are legitimate enough, from the standpoint of local
interests, but others appear to be unreasonable. In certain cases our motion pic-
ture industry may be justified in taking a strong and positive stand with the ob-
ject of bringing about the rectification of unfair measures. We need not be un-
duly hesitant. Our producers and distributors can afford to make effective their
opposition to merely narrow-minded or punitive practices, while at the same time
conforming readily to rational and moderate foreign requirements. In any such
stand they will have the backing of one momentous factor — namely, the avidity of
foreign audiences to see and hear our magnificent entertaining films.

Foreign markets play a highly significant role in the success of our motion pic-
ture industry. They must be constantly cherished and cultivated, and energeti-
cally safeguarded. It is noted that any strong wave of nationalistic sentiment in
Central Europe, finding expression in restrictive laws affecting motion pictures —
or a movement toward control or rigid censorship somewhere in Asia — or some
inimical reaction in a Latin- American country — may contribute to an ultimate
effect whereby motion picture engineers might find less in their pay-envelopes or
might even be confronted by more severe effects.

The steady efforts of the Bureau of Foreign and Domestic Commerce to safe-
guard and augment American motion picture markets by supplying a wealth of
factual data and utilizing a variety of trade-promotive methods are covered in the
paper presented. The Bureau's motion picture unit has recently been raised to
full divisional rank, in recognition of the industry's importance. Such helps as it
provides are especially vital at the present moment because, under the circum-
stances existing today, our motion picture producers and distributors are likely to
find themselves puzzled, entangled, or thwarted by the ever-growing intricacy of
the conditions that they face abroad; their continued success in foreign markets
depends upon the functioning of a reliable intelligence service.

"High-Speed Motion Picture Photography Applied to Design of Telephone
Apparatus;" W. Herriott, Bell Telephone Laboratories, Inc., New York, N. Y.

High-speed motion pictures are employed at Bell Telephone Laboratories as a
visual aid in the study of problems associated with the design, manufacture, and
testing of telephone apparatus. A new high-speed camera of the optical compen-
sator type operating at 4000 pictures per second is described, and its application
to the study of problems associated with telephone apparatus is discussed.

"Further Progress in Film Storage;" J. G. Bradley, The National Archives,
Washington, D. C.

Research has continued along the lines indicated by previous tests and reported
at the Hollywood Convention of the Society. It has been determined that the
cascade type of storage cabinet has certain advantages and may be relied upon
satisfactorily to control film fires in a cabinet having a capacity of ten reels.

A new method combining the advantages of insulation and cooling agent, while
retaining the unit isolation features, is in the process of development, and a pre-
liminary report will be presented. Stainless steel insulated cabinets are now in-
stalled at The National Archives.

Nov., 1937] • FALL CONVENTION 561

"The Effect of the Composition of an MQ Developer on Its Reduction Poten-
tial;" R. M. Evans and W. T. Hanson, Jr., Kodak Research Laboratories, Roches-
ter, N. Y.

A short time ago it was found that the reduction potential of a photographic
developer solution could be measured electrochemically. The potential is read
by dipping a platinum electrode into the solution and balancing the potential thus
set up against a standard saturated calomel half -cell by means of a potentiometer.
The addition of a potential mediator to the solution hastens the attainment of an
equilibrium and greatly facilitates making the readings without affecting the final
equilibrium.

This new tool of research has led to an extended study of the correlation be-
tween the photographic action of various developer solutions and compounds and
the electrochemical reduction potential. The results are of great theoretical and
practical interest. Knowledge of the reduction potential of a developer solution
is, however, not at all sufficient to describe its photographic properties. Reasons
for this are given, and possible uses for the measurements in practice are discussed
briefly.

In this paper the authors discuss the MQ developers and the effects of the
various constituents upon their reduction potentials. Studies have been made on
mixtures of elon and hydroquinone as well as on the two components separately,
with regard to the effect of />H, types of alkali present, concentration, sulfite and
bromide, and the presence of other reducing agents. Mixtures of elon and hydro-
quinone give a greater reduction potential than either alone, a maximum being
reached when the mol ratio is approximately 1 elon to 3 hydroquinone. The re-
sults are easily explained upon a physicochemical basis. The photographic
effects of the above variations are now being studied.

"A Modern Motion Picture Laboratory;" C. L. Lootens, Republic Productions,
Inc., North Hollywood, Calif.

A complete description of the new laboratory of the Consolidated Film Indus-
tries, Inc., which was completed during the winter 1936-37. Included are layouts
and pictures of equipment in the basement, first, and second floors. The de-
scription of the laboratory and equipment follows the sequence of operation of
negative development, "dailies," master and release printing, together with a
description of the special printers, processing units, chemical system, silver re-
covery system, and other mechanical items of interest.

"Modulated High-Frequency Recording as a Means of Determining Condi-
tions for Optimal Processing;" J. O. Baker and D. H. Robinson, RCA Manu-
facturing Co., Inc., Camden, N. J.

The quality of variable-width sound records depends to a great extent upon
image definition. The requirements, therefore, for a perfect sound-track are com-
plete transparency in the clear portion, complete opacity in the dark portions, an
extremely sharp boundary between the clear and dark portions, and exact dupli-
cation of the wave traced upon the track by the galvanometer.

Distortion is introduced by any change in the average transmission in recording
high-frequency waves. At high densities the average transmission is reduced,
and at very low densities the average transmission is increased by the presence of

562 FALL CONVENTION [J. S. M. p. E.

the high-frequency waves. The average transmission is compared to the trans-
mission through the film for a 50 per cent exposed track without signal.

It is possible, therefore, to find a density at which there is little, if any, change
in average transmission, and this density corresponds to the most nearly perfect
image definition and the least distortion. On an original or negative recording,
with the present commercial recording stocks, this density is extremely low, being
of the order of 0.6 to 0.8. For the least amount of ground-noise, the negative
must be recorded at a much higher density. A change in the average transmission
of the negative can be tolerated, since by the proper choice of print density, a
condition of minimum distortion in the positive track can be attained.

A modulated high-frequency recording affords an extremely accurate method of
determining the correct negative and print densities for any given conditions of
laboratory processing. An oscillator, designed for several carrier frequencies, is
provided with a 400-cycle modulator for recording. The modulated carrier is
recorded for several values of lamp current and processed to give a number of
negative densities. Prints are then processed at various values of densities, and
the 400-cycle output measured on suitable reproducing equipment. The com-
bination of negative and print densities that gives the least amount of 400-cycle
output indicates the condition for best image definition and least distortion.

Care must be exercised in the design and construction of the oscillator to main-
tain the 400-cycle output to a minimum.

"Possibilities of Stereoscopic Motion Pictures;" G W. Wheelwright, 3d,

Land-Wheelwright Laboratories, Inc., Boston, Mass.

The historical background of three-dimensional motion pictures is first dis-
cussed, leading up to the requirements of true stereoscopy and a discussion of some
of the factors involved, such as overlap, detail, apparent sizes of objects, haze,
lighting effects, and two-eye pictures taken eye distance apart. Serious three-
dimensional work falls into two classes: (a) critical-angle stereoscopy, and (i)
anaglyph stereoscopy. Under the latter heading falls the use of colors to achieve
stereoscopic effects, as in Lumiere's work, and Audioscopics, which have several
disadvantages; also polarizing anaglyphs, first operated by Anderton in 1893,
and most recently through the use of Polaroid.

Advantages to be gained from three-dimensional pictures in color as opposed to
single pictures using the same color system are explained. Some of the problems
of photographers and theaters in using the Polaroid system are discussed, followed
by a discussion of the advantages of stereoscopic pictures in dramatic delineation.

"Distortion in the Reproduction of Hill-and-Dale Recording;" M. J. Di Toro,

Research Dept. of Ediphone Division, Thomas A. Edison, Inc., West Orange, N. J.
In the reproduction of a hill-and-dale recording, the curve traced by the re-
producer stylus differs from the recorded curve, with the consequent introduction
of both frequency and amplitude distortion. This distortion is called "tracing
distortion," and must be tolerated only in virtue of the physical necessity of a
finite tip radius for the reproducer stylus. Curves and formulas are given for
the quantitative determination of the harmonic generation and decay in funda-
mental due to tracing distortion as functions of the amplitude and frequency of
the recorded undulation, the linear groove speed, and the tip radius of the repro-

Nov., 1937] FALL CONVENTION 563

ducer stylus. It is shown that for "constant-velocity" recordings, when the
minimum radius of curvature of the recorded undulation is equal to or larger than
5 times the tip radius of the reproducer stylus, the rms. harmonic generation is
at most 10 per cent. Moreover, the generation of harmonics is a much more
serious limitation upon the quality of the reproduction than is the decay of funda-
mental frequency, as, for example, in cases where the loss of fundamental is only
2 db., this harmonic generation is prohibitively high, being much greater than 10
per cent.

"Recent Developments in Hill-and-Dale Recorders;" L. Vieth and C. F.
Wiebusch, Bell Telephone Laboratories, Inc., New York, N. Y.

A new sound-on-disk recorder has been developed in which is used the principle
of feeding part of the output of the system back to the input of the associated
driving amplifier in properly controlled relationship. The use of this principle,
which is widely used in feedback amplifiers, replaces the usual practice of provid-
ing dissipative elements for the control of an electrically driven vibrating system.
Heretofore no practical application of feedback to electromechanical systems has
been made, possibly because the requirements for stable operation of such sys-
tems are difficult of achievement. Through recent developments these require-
ments have been satisfactorily met. The new recorder is capable of recording on
wax or direct recording material without any effect upon its characteristics,
which include uniform response from 30 to 12,000 cps. and exceptional freedom
from distortion products. The recorder is extremely simple and affords easy
means for field calibration from the feedback element whose output is in direct
proportion to the stylus velocity. These means also make available a monitoring
voltage, which, properly amplified, gives a precise aural picture of the stylus be-
havior during recording.

"Film Perforation and 96-Cycle Frequency Modulation in Sound-Film Rec-
ords;" J. Crabtree and W. Herriott, Bell Telephone Laboratories, Inc., New York,
N. Y.

When motion picture film is flexed around a cylinder, the film in the region of
the sprocket-holes does not follow a smooth curve. In a sound record this leads
to frequency distortion of perforation frequency.

"Suggested Standard Nomenclature for Release Print Sound-Tracks;" J. K.
Milliard, Metro-Golden-Mayer Studios, Culver City, Calif.

A general description of the following types of movietone sound-track, which
are currently being released or will be released in the immediate future according
to plans:

(1) Standard movietone; (2) standard movietone with squeeze- or matted-
track; (5) standard movietone with double-squeeze or matted-track ; (4) movie-
tone push-pull; (5) movietone push-pull squeeze or matted-track; (6) variable-
width bilateral with bias ; (7) variable-width bilateral with shutter; (8) variable-
width unilateral bias track; (9) variable- width push-pull.

During the past year all the above-mentioned tracks have been used to some
extent in released movietone pictures. The paper shows samples of the various

564 FALL CONVENTION [J. S. M. p. E.

types of tracks and gives a general description of their characteristics. A descrip-
tion is also included of the general technic involved in recording and reproducing
the so-called "hot and cold" or "A and B" prints. During the past two years this
particular type of print has been used very successfully in extending the volume
range of the variable-density release to approximately 50 db. This release is
intended to be shown only in theaters having equipment adequate to reproduce
music 6 to 10 db. higher than average dialog.

A description of the mechanics and technic for re-recording using the squeeze-
track is outlined. This procedure increases the noise reduction from 3 to 6 db.,
depending upon the amount of squeeze applied.

"Air-Conditioning with Lithium Chloride;" G. A. Kelley, Surface Combustion
Corporation, Toledo, Ohio.

A system of air-conditioning is described that employs lithium chloride for inde-
pendently controlling both the relative humidity and the dry-bulb temperature of
air. It is used both for comfort air-conditioning and for treating air for indus-
trial processing work.

Lithium chloride is one of the most hygroscopic of inorganic compounds, and
the aqueous solution has the property of absorbing moisture from, or adding
moisture to, the air, depending upon the vapor pressure difference between the
air and the solution. From this it is seen that, by properly controlling the con-
centration and temperature, the lithium chloride solution is capable of either
dehumidifying or humidifying the air, depending upon the requirements. The
air is cooled or warmed when passed over an aqueous solution of lithium chloride,
depending upon whether the solution is cooler or warmer than the air. Further
cooling or warming of the air when desired is attained by using an after-cooling or
after-heating coil.

The cycle of air-conditioning is explained and illustrations of an air-conditioning
unit are shown. The application of the system to a typical problem of interest
to motion picture engineers is discussed and illustrated by means of a schematic
flow diagram. Operating data for full-load and for less than full-load conditions
show low cost of operation and efficiencies equally as high when operating either
at maximum load or at less than maximum load. Washing, deodorizing, and
neutralizing bacteria from the air by contact with lithium chloride are important
factors where pure clean air is desired.

"The Activated Alumina System as Applied to Air-Conditioning and Drying
Problems;" G. L. Simpson, Pittsburgh Lectrodryer Corp., Pittsburgh, Pa.

The phenomenon of adsorption is discussed. Some of the properties of the
solid adsorbent, activated alumina, are given.

A dynamic characteristic curve of the adsorbent is included. This charac-
teristic is utilized industrially to dry air and gases to dewpoints as low as —76°
C (0.0004 grain per cubic foot; 0.0009 milligram per liter). Apparatus utiliz-
ing activated alumina in this way is described and illustrated.

Uses include the drying of controlled atmospheres, bottling gases, and in
chemical processing when water vapor would promote corrosion or adversely
effect the process. Compressed-air lines are kept free of water to prevent freezing
in winter or spoilage of work.

Nov., 1937] FALL CONVENTION 565

In industrial and comfort air-conditioning, comparatively large quantities of
partially dried air are required. A continuous dehumidifier to meet these re-
quirements is described and illustrated.

Performance is a function of machine design as well as of fundamental charac-
teristics of the solid adsorbent used. Depending upon factors of first cost and
economy of operation, a wide range of characteristic performance may be
obtained. A curve shows the present-day characteristic of a line of machines
commercially available.

The humidity in storage rooms and processing departments may be reduced by
the simple installation of one of these machines without auxiliary equipment.
Combined with cooling and circulation these dehumidifiers may be used effectively
in summer air-conditioning installations in industrial and comfort applications.

In the manufacture of film base, water vapor may be deposited in the material
by cooling due to solvent evaporation. This is avoided by using dehumidified air
in the process.

Some substances can not be heated much above room temperature without
damage. Humid summer air has too high an absolute humidity to accomplish
satisfactory drying without raising the temperature beyond this limit. De-
humidified air fed to drying cabinets or tray dryers solves the problem. Uni-
formity of drying conditions may also be achieved by controllably dehumidifying
the input air to drying systems.

"Die Castings and Their Application to Photographic Appliances;" J. C. Fox,
Doehler Die Casting Co., Toledo, Ohio.

Die castings are defined as castings made by forcing molten metal into a metallic
mold or die. The alloy most generally used is of the zinc base type, having a
tensile strength of approximately 40,000 Ibs. per sq. inch. For photographic
appliances, the alloys of lower specific gravity are more desirable. Aluminum
base alloys are used more extensively in photographic appliances for that reason.
Physical properties of various aluminum die casting alloys are given.

Since low specific gravity is of prime importance in castings used for photo-
graphic appliances, the development of the process of die casting the lightest of all
commercial metals, magnesium, is of particular interest to motion picture engi-
neers. Magnesium is one-third lighter than aluminum, and magnesium die cast-
ings are now being used wherever light weight is important. Physical properties
of magnesium die castings are given. Reference is also made to the die casting
of brass and German silver, recently developed.

Report of the Standards Committee; E. K. Carver, Chairman.

There have been but two meetings of the Standards Committee since the last
report. During the summer, fourteen new drawings have been completed, cover-
ing 8-mm. film standards, revision of the drawings for sprockets, and reels for
35-mm., 16-mm., and 8-mm. film, but only preliminary discussion of them has
occurred.

The Standards Committee has given initial approval to the dimension 0.15 mm.
for the space separating the two halves of the push-pull sound-track, but the
balloting is not yet complete.

566 FALL CONVENTION [J. S. M. P. E.

"The Use of Inconel for Photographic Film-Processing Equipment;" G. L.

Cox, International Nickel Co., New York, N. Y.

The general corrosion resistance of Inconel, making it useful in film processing,
is discussed. Typical applications with significant service data are described.
Special reference is made to the outstanding usefulness of Inconel in the prepara-
tion of the sensitized plate, fixing, toning, intensification, and reduction opera-
tions. The well established uses of nickel and Monel for developing operations
are briefly discussed.

"Newer Types of Stainless Steel and Their Applications to Photographic
Processing Equipment;" H. A. Smith, Republic Steel Corp., Massillon, Ohio.

Within the last three years, two new types of stainless steel have been de-
veloped: (1) type 515 which contains approximately 18% chromium, 8% nickel,
1.5% copper, and 1.5% molybdenum; and (2) a modification of type 316 (the
usual 18-8S Mo) where the molybdenum content has been raised to from 3 to 4%
molybdenum. Considerable test data are now available for type 329, containing
approximately 27% chromium, 4.5% nickel, and 1.5% molybdenum. The latter
steel shows promise in that pit-corrosion tendency is considerably reduced.
Satisfactory welds may also be made with this type. From the corrosion-resisting
standpoint, three other compositions are discussed: type 309, 24% chromium,
13% nickel; type 310, 25% chromium, 20% nickel; and type 446, 27% chromium.

Electrochemical potential curves are given showing the behavior of these types
of steel in hypo and developer solutions. A table of the position of these stainless
steels in the electrochemical potential series is given.

It is pointed out that a polished (No. 6) and a finely ground (No. 4) finish are
more corrosion-resistant than a pickled finish, not only from the potential stand-
point but due to the decreased possibility of their collecting foreign matter that
will accelerate corrosive attack.

"Vacuum-Tube Engineering for Motion Pictures;" L. C. Hollands and A. M.
Glover, RCA Radiotron Division, RCA Manufacturing Company, Inc., Harrison,
N.J.

Manufacturing and developmental technics of vacuum tubes are described with
particular reference to their use in motion picture equipment. A brief discussion
of how application requirements affect the choice of materials, structural design,
and electrical characteristics of phototubes and amplifiers of both power and
voltage types is included. How tubes are designed to meet specific needs is
illustrated by reference to recent tube developments. Work on producing tubes
having low-hum, low-microphonic, and low-noise characteristics is described as of
special interest to the motion picture engineer. The paper closes with recom-
mendations as to how to use vacuum tubes to best advantage.

" Spectral Distributions and Color-Temperatures of the Radiant Energy from
Carbon Arcs Used in the Motion Picture Industry;" F. T. Bowditch and A. C.
Downes, National Carbon Co., Inc., Cleveland, Ohio.

Color-temperatures of various carbon arcs have been calculated from spectral
energy data. The dominant wavelength and per cent purity of each arc are
given with reference to both "average daylight" and "noon June sunlight."

Nov., 1937] FALL CONVENTION 567

It is pointed out that the color-temperatures of these carbon arc light-sources
are of value in comparing them upon a visual basis only. The effects of the
radiant energy from the arcs upon any photosensitive medium other than the
human eye (for example, photographic film) are very different from the visual
impression.

Spectral energy distribution curves of several carbon arc sources are published
for the first time.

" Recent Developments in Background Projection;" G. G. Popovici, New York,

N. Y.

The complexity of the background projection process is generally known. It
has been widely applied in cinematography with great success. A new field
offers tremendous opportunity, namely, still photography. Two types of back-
ground projectors are described, one to cover screens up to 10 X 12 feet, the other
to cover screens up to 13 X 18 feet. During the research stage, some very inter-
esting facts have been observed. The following elements of the problem are
discussed :

(1) The spot condition: what causes it and how to reduce it successfully, even
eliminating it entirely in specific cases. (2) Screen textures: nitrate or acetate
base sprayed with polarizing material for diffusion (flatlight type); the new
Trans-Lux screen of the high-transmission type. (3) Theory of light refraction
through screen. (4) Light brightness vs. diffusion of screen. (5) Optical condi-
tions, condensers, objective lenses, etc. (6) Light-source proper: brightness vs.
current, behavior of different types of carbons; spectral consideration in color
projection. (7) Cooling the slides with air, a novel method incorporating re-
frigerated air for the super-pro jectoi. (5) Projector electrical, optical, air-oper-
ating characteristics, including remote control of arc, douser, air-cooling system.

"A Method of Enlarging the Visual Field of the Motion Picture Screen;" B.

Schlanger, New York, N. Y.

Recent trends toward the smaller sized motion picture audience indicate that
new considerations can be given to the possibility of a larger and differently
shaped screen, retaining the 35-mm. film. The screen is pictured as completely
occupying the entire forefront of the motion picture auditorium, becoming a space
stage instead of an artificially framed picture.

"Recent Developments in Gaseous Discharge Lamps;" S. Dushman, Research
Laboratory, General Electric Company, Schenectady, N. Y.

The luminous and electrical characteristics of a number of vapor discharge
lamps which have attained practical importance in recent years are described.
These include the sodium vapor lamp, the high-intensity mercury vapor lamp,
and the high-pressure quartz capillary lamp. The fundamental physical phe-
nomena and the manner in which these effect the light output and efficiency are
discussed briefly. The effect of variations in gas pressure and current density
upon the distribution of intensity in the spectrum is dealt with, and also the
accompanying changes in intrinsic brilliancy and color of light emitted.

The latter part of the paper contains a discussion of recent developments in
the utilization of fluorescent materials in gaseous discharge lamps. These lamps

568 FALL CONVENTION [J. s. M. P. E.

offer interesting possibilities from the point of view of general illumination and
special color effects.

Report of the Studio Lighting Committee; R. E. Farnham, Chairman.

The past year has witnessed unusual advances in both studio lighting equip-
ment and technic of lighting, second only to the famous 1928 period when the
studios adopted incandescent lighting.

Cameramen are entering an era of "precision" lighting. Highlights and
shadows are carefully balanced with dimmers as well as by placement of the units.
This calls for equipment giving more accurate light control. The influence of
lighting for color is creating a greater appreciation upon the part of cameramen of
the color-quality of the light in black-and-white photography.

The report also describes the development of a satisfactory filter of extreme
accuracy, making possible the use of incandescent lamps of the CP type for Techni-
color photography, either alone or when mixed with other suitable illuminants.

"Grading Projectionists;" G. P. Barber, Government of the Province of Alberta,
Edmonton, Alberta, Canada.

Advanced methods of licensing projectionists in the Province of Alberta are
described, with some comments on the apparent benefits derived from the process.
The process of becoming a first-class projectionist requires a licensed apprentice-
ship of at least twelve months, followed by one year as third-class and, later, one
year as second-class projectionist before taking final examination for a first-class
license. Each period, except apprenticeship, is preceded by a thorough examina-
tion.

" CoSperation as the Keynote of Projection Service;" T. P. Hover, Warner's
Ohio Theater, Lima, Ohio.

It has been pointed out that engineers as a group are backward in dealing with
problems involving the human element. They would rather deal with things
than persons. They can not be blamed for this attitude, however, because most
engineering problems can be solved by definite formulas and procedures, while
problems dealing with the human element seldom follow the expected path.

This human element is a vital consideration in the successful operation of a
theater that requires that sound and projection equipment be maintained in first-
class condition at all times.

Plans and ideas that have aided us in maintaining a high standard of projection
in Lima are presented. Since the city is more than 150 miles from the nearest
parts-supply company, a well planned system of mutual cooperation is of the
greatest importance in order to prevent shut-downs with attendant loss of money
and good-will. The success of the plans over a period of ten years recommends it
to the consideration of other projectionists' organizations that are more or less
isolated from repair and emergency engineering facilities.

A Discussion of Screen-Image Dimensions; F. H. Richardson, New York,
N. Y.

An argument is presented for recommended standard screen-image proportions
based upon the dimensions and brightness that will provide most comfortable
viewing conditions at the center of the theater seating space. It proposes that

Nov., 1937] FALL CONVENTION 569

such compromise would tend to best average viewing conditions and, therefore,
least eye-strain and most enjoyment for the audience as a whole.

"Precision All-Metal Reflector for Use with Projection Arcs;" C. E. Shultz,
Heyer-Shultz, Inc., Montclair, N. J.

The peculiar characteristics of an all-metal reflector are discussed regarding its
resistance to tarnish, pitting, breakage, and heat. Comparison is made between
the present standard glass reflector and this new type as to reflectivity, dependa-
bility, accuracy, color-response, and longevity.

"Perforated Screens and Their Faults;" F. H. Richardson, New York, N. Y.

Certain faults of perforated screens are discussed, particularly with relation to
imperfection in perforations. The question is raised as to what extent the faulty
perforations, as illustrated by slides, may be detrimental to sound quality in
theaters.

"Commercial Sixteen-Millimeter Projection Faults;" C. L. Greene, Minneapo-
lis, Minn.

Because commercial motion pictures on 16-mm. film are an outgrowth of "home
movies," the standards of projection are low. Less care is given to their proper
presentation than in the case of theatrical showings of 35-mm. film; whereas,
because of the greater overall magnification, greater care should be given. Some
of the more glaring faults are treated in detail, a general treatment is set forth,
and the importance of proper presentation is clarified by comparison of show-
windows of the street and of the screen.

"The Sound-Level Meter in the Motion Picture Industry;" H. H. Scott and
L. E. Packard, General Radio Company, Cambridge, Mass.

The modern sound-level meter may be used as a convenient means for making
a large number of measurements of value to the motion picture industry. Recent
designs featuring light weight, small size, and convenience of control make modern
sound-level meters particularly well adapted for such purposes.

Among the many possible uses are: measuring noise-levels in studios and
theaters ; measuring noise made by ventilating equipment, cameras, or projection
equipment; measuring background noise-level from reproducing system; check-
ing overall frequency response of reproducing system; checking variation in
frequency -response throughout auditorium; checking level of reproduction in
auditorium; etc. Typical data are presented showing results obtained in a
theater.

"New Ideas in Mobile Sound-Recording Equipment;" J. G. Matthews and
C. M. Ralph, General Service Studios, Inc., Hollywood, Calif.

An extensive rental service, in addition to the usual studio facilities, has created
at General Service Studios, Inc., a demand for sound-recording equipment that is
unusually broad in scope. Portability requirements range from completely port-
able "trunk" equipments to mobile recording and re-recording rooms having a high
degree of comfort and convenience. Operating requirements impose the need
for twenty-four-hour-per-day service, at times, from any one of a number of

570 FALL CONVENTION [J. S. M. p. E.

power sources. At the same time, in consideration of the rentrl aspect, sim-
plicity and fool-proof operation were found to be essential.

The requirement for a mobile recording room has been met very economically
and advantageously by the use of a cabin type of trailer. Features of the equip-
ment are: complete operation from a-c. supply on the lot, darkroom facilities,
simplicity of operation, adequate storage space, comfort, and appearance. The
multiple-channel re-recording trailer is designed along similar lines and is a versa-
tile unit which, with its signaling and remote control systems, permits its use
with all other recording equipment to form a complete channel.

The requirements for all degrees of portability on location work have been
excellently met by the adaptation of a portable recording channel to a two-ton,
standard-body truck. From a utility standpoint this channel incorporates many
design features that make its use highly desirable for this class of service. The
recording console is standard with that in the recording trailer. An internal
battery-motor-generator power-supply allows three-day location operation with-
out recharging. When available, three-phase alternating current allows full
channel and motor system operation for any length of time desired. Channel
operation is possible on single-phase alternating current. Three-phase motor
systems expedite recording. The equipment is removable from the truck for
extreme, "trunk" channel portability. Changes from one recording condition to
another are accomplished by one master switch.

Such novel features as have been incorporated in the trailer and truck equip-
ment seem, thus far, to have been well justified.

"A Mobile Sound-Recording Channel;" L. T. Goldsmith and B. F. Ryan,
Warner Brothers Pictures, Inc., Burbank, Calif.

A location-truck recording channel is described that incorporates the latest
equipment and operating features. All the advantages and facilities of a fixed
installation are retained in the unit without sacrificing its mobility or simplicity
of operation.

The equipment used was built for Warner Bros, by the RCA Manufacturing
Company. Recordings are of either the standard bilateral or push-pull variable-
width type, and are made using ultraviolet exposure of the film. High-quality
circuits are used from microphones to the recording machine. Monitoring is
accomplished with high-speed volume indicators and high-fidelity head-phones.

Facilities are provided for operating the portable mixer case either inside the
truck or remotely at distances up to 1000 feet. A collapsible duralumin micro-
phone pole is carried, and several wind and rain screens are provided to permit
recording under adverse conditions.

Disk or film playback equipment can be operated from the truck and recordings
made at normal road speed if desired. The unit is quiet in operation so that it
may be used close to the action on the set.

"A Device for Cleaning the Sound-Track of Motion Picture Film during
Projection;" R. J. Fisher, Flower City Specialty Co., Rochester, N. Y.

A description is given of a device for cleaning the sound-track or zone on which
sound is recorded. It comprises a compact attachment applicable to all existing
projectors without alteration of the projector mechanism, which is simple and

Nov., 1937] FALL CONVENTION 571

sturdy in operation. Its object is to improve the reproduction of recorded sound
by removing completely all dirt, dust, and lint lodging on the sound-track during
the process of projection, rewinding, and shipping.

"Reduction of Loop-Length Variations in Non-Slip Printers;" E. W. Kellogg,
RCA Manufacturing Co., Inc., Camden, N. J.

Compensation for varying degrees of film shrinkage is accomplished in the
Bedford non-slip printer by changes in the length of a loop of film between a
sprocket and the printing point. This involves uncertainty of synchronism by
the amount that the loop, as first threaded, differs in length from the final running
loop. For most purposes, the present designs do not cause more change in loop-
length than may be readily tolerated.

For certain purposes, especially if this type of printer is to be employed for 16-
mm. films, there may be too much departure for synchronism. A guide-roller
arrangement is described by which the necessary change of angle of approach of
the raw stock to the printing point is attained with comparatively small change
in loop-length.

Several possible arrangements are considered and some other features of the
non-slip printer are discussed.

"A Recorder for Making Buzz-Track;" E. W. Kellogg, RCA Manufacturing
Co., Inc., Camden, N. J.

The only requirements of a buzz-track are that the track be of correct width and
properly located with respect to the edge of the film nearest the track, and that
the sound produced by a weave in one direction shall be readily distinguishable
from that which results when the film is displaced in the other direction.

It is better that the buzz-track film should be a direct recording rather than a
print, since there is less chance of inaccurate location. A simple recorder has been
constructed for the sole purpose of making buzz-track film. It can readily be
converted for 16-mm. All possible precautions are taken to insure correct track
width and location.

In view of the small quantity of buzz-track required, it is contemplated that
only one such machine will be needed.

"Recording Tests on Some Recent High-Resolution Experimental Emulsions;"
J. O. Baker, RCA Manufacturing Co., Inc., Camden, N. J.

The effect of, and conditions for, image definition in variable-width sound-
recording are discussed in a separate paper, "Modulated High-Frequency Record-
ing as a Means of Determining Conditions for Optimal Processing," also presented
at this Convention. There it is shown that the present commercial sound-re-
cording emulsions have the least distortion at very low density, accompanied by
an undesirable amount of ground-noise if used as a positive.

A new experimental emulsion, E.K. 0-7461-1, differs from present emulsions in
that it has extremely high resolution and minimum distortion at a density of
approximately 1.5.

The speed of this emulsion is less than that of regular recording stocks, but
since it is used with white light and no filter is required, sufficient densities are
readily attained with present optical systems. These characteristics offer possi-
bilities heretofore not attainable.

572 FALL CONVENTION

The high-resolution, low image-spread and low film-hiss of this emulsion makes
possible recording a positive sound-track that can be played directly, thus elimi-
nating the distortion usually introduced in the printing process and the ground-
noise contributed by the negative.

The advantage of using this emulsion for direct playbacks will be realized
whether the recording is standard, Class A push-pull or Class B push-pull. The
inherent perfection of image definition in the new emulsion means increased proc-
essing tolerances in adjusting the Class B system for perfect cross-over between
the negative and positive half -waves.

It is not at present feasible to use this emulsion as a negative for making prints
on positive stock. For special sound-films without pictures, the new emulsion
may be used for a printed positive, using a negative made on the same stock, pro-
vided the printer losses are not excessive.

SOCIETY ANNOUNCEMENTS

BOARD OF GOVERNORS

Final details for the Convention (just ended) were completed at the meeting
of the Board of Governors on October 10th at the Hotel Pennsylvania, New York,
N. Y. The report of the Financial Vice-President indicated that the finances of
the Society were proceeding in a satisfactory manner and that the growth of
membership reported herein from time to time was continuing apace. The
Secretary reported that the Society had been qualified for doing business through
its recently established office in the State of California.

Reports were presented to the Board from the Admissions Committee and
the special committee established to investigate the present nomination pro-
cedure. The question of microfilm standardization was also discussed, as well
as the relation of the Non-Theatrical Equipment Committee to motion picture
standardization in the educational field.

The next Convention has been scheduled for Washington, D. C., headquarters
at the Wardman Park Hotel, April 25th to 28th, inclusive.

PROGRESS AWARD

At the Semi-Annual Banquet of the Society held at the Hotel Pennsylvania
on October 13th, the annual Award of the SMPE Progress Medal was made to
E. W. Kellogg of RCA Manufacturing Company, Camden, N. J. Previous re-
cipients of the Progress Medal were: 1935, E. C. Wente, Bell Telephone Labora-
tories, New York, N. Y.; 1936, C. E. K, Mees, Eastman Kodak Company,
Rochester, N. Y.

JOURNAL AWARD

The presentation of the annual SMPE Journal Award was made at the Semi-
Annual Banquet on October 13th to D. B. Judd, of the National Bureau of
Standards, Washington, D. C., for his paper entitled "Color Blindness and
Anomalies of Vision," published in the June, 1936, issue of the JOURNAL. The
Award consisted of an engrossed certificate accompanied by a cash award of $50.

In addition, the Journal Award Committee cited the following papers for
Honorable Mention:

"Improved Resolution in Sound Recording and Printing by the Use of Ultra-
violet Light," G. L. Dimmick (Aug., 1936).

"Continuous Photographic Processing," H. D. Hineline (Jan., 1936).

OFFICERS FOR 1938

As a result of the recent election of Officers for 1938, the ballots having been
counted on the first day of the recent Convention (October llth), the following
is the list of Officers for the coming year:

573

574 SOCIETY ANNOUNCEMENTS

*Executive Vice- President: K. F. Morgan
** Engineering Vice- President: L. A. Jones
**Financial Vice- President: E. A. Williford

^Secretary: J. Frank, Jr.

* Treasurer: L. W. Davee

** Governors: R. E. Farnham, H. Griffin, A. C. Hardy

Officers and Governors of the Society who continue in office for another year
are as follows:

*President: S. K. Wolf

* Past-President: H. G. Tasker
^Editorial Vice- President: J. I. Crabtree

* Convention Vice- President: W. C. Kunzmann
^Governors: M. C. Batsel, A. N. Goldsmith

SOCIETY SUPPLIES

The following are available from the General Office of the Society, at the prices
noted. Orders should be accompanied by remittances.

Aims and Accomplishments. — An index of the Transactions from October,
1916, to December, 1929, containing summaries of all articles, and author and
classified indexes. One dollar each.

Journal Index. — An index of the JOURNAL from January, 1930, to December,
1935, containing author and classified indexes. One dollar each.

SMPE Standards. — Reprints of SMPE Standards and Recommended Practice.
Twenty-five cents each.

Membership Certificates. — Engrossed, for framing, containing member's name,
grade of membership, and date of admission. One dollar each.

Lapel Buttons. — The insignia of the Society, gold filled, with safety screw back.
One dollar each.

Journal Binders. — Black fabrikoid binders, lettered in gold, holding a year's
issue of the JOURNAL. Two dollars each. Member's name and the volume
number lettered in gold upon the backbone at an additional charge of fifty cents
each.

Test- Films. — See advertisement in this issue of the JOURNAL.

Term expires December 31, 1938.
Term expires December 31, 1939.

S. M. P. E.

STANDARD TEST-FILMS

These films have been prepared under the supervision of the Projection
Practice Committee of the Society of Motion Picture Engineers, and are
designed to be used as precision instruments in theaters, review rooms,
exchanges, laboratories, factories, and the like for testing the perform-
ance of projectors.

Only complete reels, as described below, are available (no short sections
or single frequencies). The prices given include shipping charges to all
points within the United States; shipping charges to other countries are
additional.

35-Mm. Sound-Film

Approximately 500 feet long, consisting of recordings of several speak-
ing voices, piano, and orchestra; buzz-track; fixed frequencies for focus-
ing sound optical system; fixed frequencies at constant level, for de-
termining reproducer characteristics, frequency range, flutter, sound-
track adjustment, 60- or 96-cycle modulation, etc.

The recorded frequency range of the voice and music extends to 10,000
cps.; the constant-amplitude frequencies are in 15 steps from 50 cps. to
10,000 cps.

Price $37.50 each, including instructions.

35-Mm. Visual Film

Approximately 500 feet long, consisting of special targets with the aid
of which travel-ghost, marginal and radial lens aberrations, definition,
picture jump, and film weave may be detected and corrected.

Price $37.50 each, including instructions.

16-Mm. Sound-Film

Approximately 400 feet long; contents identical to those of the 35-mm.
sound-film, with the exception that the recorded frequency range ex-
tends to 6000 cps., and the constant-amplitude frequencies are in 11
steps from 50 cps. to 6000 cps.

Price $25.00 each, including instructions.

16-Mm. Visual Film

. An optical reduction of the 35-mm. visual test-film, identical as to
contents and approximately 400 feet long.
Price $25.00 each, including instructions.

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA
NEW YORK, N. Y.

I

When you book an expensive, nation-
ally famous feature, you are planning
to cash -in on people's expectations.
You are planning to impress them —
not to disappoint them.

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with big features, and especially with
color.

The only way to deliver the goods
is the same way 5000 theaters are now
doing it — with high intensity projec-
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Almost any house can now afford
modern projection. New SIMPLIFIED

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double or triple screen brightness at so
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Write for the new, free, illustrated
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Unit of Union Carbide ITPR and Carbon Corporation

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Copyright 1937, National Carbon Company, Inc.

II

Society of Motion Picture Engineers

HOTEL PENNSYLVANIA
NEW YORK, N. Y.

APPLICATION FOR MEMBERSHIP

APPLICANT'S RECORD

Name Age. . .

Mailing Address

Permanent Address ,

Present Occupation ,

Employer

A complete account of the applicant's qualifications and accomplishments is
required before an application may be submitted to the Board of Governors.
The applicant should describe any inventions and improvements he has made
in the art, as these are considered of more importance than a mere record of
experience or the names of positions the applicant has filled.

Education

Record of Accomplishments.

Motion Picture Experience.

Grade Applied For.

REFERENCES

3.

2.

The undersigned certifies that the above statements are correct, and agrees,
if elected to membership, that he will be governed by the Society's Constitution
and By-Laws so long as his connection with the Society continues.

Date 19. .. Signed

(Use a separate sheet of paper for complete record of accomplishments)

Statement of the Ownership, Management, Circulation, Etc., Required by the

Acts of Congress of August 24, 1912, and March 3, 1933, of Journal of the Society

of Motion Picture Engineers, published monthly at Easton, Pa., for October 1,

1937.

State of New York 1

County of New York / s'

Before me, a Notary Public in and for the State and County aforesaid, person-
ally appeared Sylvan Harris, who, having been duly sworn according to law,
deposes and says that he is the Editor of the Journal of the Society of Motion
Picture Engineers and that the following is, to the best of his knowledge and
belief, a true statement of the ownership, management (and if a daily paper,
the circulation), etc., of the aforesaid publication for the date shown in the above
caption, required by the Act of August 24, 1912, as amended by the Act of
March 3, 1933, embodied in section 537, Postal Laws and Regulations, printed
on the reverse of this form, to wit:

1. That the names and addresses of the publisher, editor, managing editor,
and business managers are:

Name of — Post Office Address —

Publisher, Society of Motion Picture Engineers, Hotel Pennsylvania, New York,

N. Y.

Editor, Sylvan Harris, Hotel Pennsylvania, New York, N. Y.
Managing Editor, Sylvan Harris, Hotel Pennsylvania, New York, N. Y.
Business Manager, Sylvan Harris, Hotel Pennsylvania, New York, N. Y.

2. That the owner is: (If owned by a corporation, its name and address
must be stated and also immediately thereunder the names and addresses of
stockholders owning or holding one per cent or more of total amount of stock.
If not owned by a corporation, the names and addresses of the individual owners
must be given. If owned by a firm, company, or other unincorporated concern,
its name and address, as well as those of each individual member, must be given) .
Society of Motion Picture Engineers, Hotel Pennsylvania, New York, N. Y.

S. K. Wolf, President, 100 E. 42nd St., New York, N. Y.

J. Frank, Jr., Secretary, 90 Gold St., New York, N. Y.

L. W. Davee, Treasurer, 250 W. 57th St., New York, N. Y.

3. That the known bondholders, mortgagees, and other security holders
owning or holding 1 per cent or more of total amount of bonds, mortgages, or
other securities are: (If there are none, so state).

None.

4. That the two paragraphs next above, giving the names of the owners,
stockholders, and security holders, if any, contain not only the list of stockholders
and security holders as they appear upon the books of the company but also,
in cases where the stockholder or security holder appears upon the books of the
company as trustee or in any other fiduciary relation, the name of the person or
corporation for whom such trustee is acting, is given; also that the said two
paragraphs contain statements embracing affiant's full knowledge and belief
as to the circumstances and conditions under which stockholders and security
holders who do not appear upon the books of the company as trustees, hold stock
and securities in a capacity other than that of a bona fide owner ; and this affiant
has no reason to believe that any other person, association, or corporation has
any interest direct or indirect in the said stock, bonds, or other securities than
as so stated by him.

5. That the average number of copies of each issue of this publication sold
or distributed, through the mails or otherwise, to paid subscribers during the
six months preceding the date shown above is: (This information is required
from daily publications only).

SYLVAN HARRIS, Editor, Business-Manager.
Sworn to and subscribed before me this 7th day of September, 1937.

(Seal) Wm. J. Miller.

Notary Public, Clerk's No. 188, New
York County. Reg. No. 8-M-13.
(My commission expires March 30, 1938)

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

Volume XXIX DECEMBER, 1937 Number 6

CONTENTS

Page
Proceedings of the Semi- Annual Banquet of the Society at

New York, N. Y., October 13, 1937 577

Propaganda, Education, and the Entertainment Film

M. QUIGLEY 592

Television Demonstration at the Fall Convention 596

Possibilities of Stereoscopic Motion Pictures

G. M. WHEELWRIGHT 603

Report of the Projection Practice Committee 614

Standardization of Photographic Densitometry

CLIFTON TUTTLE AND A. M. KOERNER 622

Notes on the Velocity Microphone M. RETTINGER 629.

Interference Effects in Rooms M. RETTINGER 635

Report of Membership and Subscription Committee 643

Symposium on Transmission Meters

A Continuous Level Recorder for Routine Studio and Theater

Measurements G. M. SPRAGUE AND J. K. HILLIARD 645

A Curve-Plotting Transmission Meter L. A. AICHOLTZ 655

A Curve-Plotting Transmission Meter L. D. GRIGNON 660

An Automatic Audio-Frequency Graphic Recorder

A. D. MACLEOD 663
New Motion Picture Apparatus

A New Type of Double-Film Attachment

E. C. MANDERFELD 669
A Combined Viewing and Projection Machine with or without

Sound I. SERRURIER 673

Current Literature 678

Society Announcements 681

Index: July-December, 1937

Author 689

Classified.. 692

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

SYLVAN HARRIS, EDITOR

Board of Editors
J. I. CRABTREE, Chairman

A. N. GOLDSMITH L. A. JONES H. G. KNOX

A. C. HARDY E. W. KELLOGG T. E. SHEA

Subscription to non-members, $8.00 per annum ; to members, $5.00 per annum,
included in their annual membership dues; single copies, $1.00. A discount
on subscriptions or single copies of 15 per cent is allowed to accredited agencies.
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y.
Published monthly at Easton, Pa., by the Society of Motion Picture Engineers.

Publication Office, 20th & Northampton Sts., Easton, Pa.
General and Editorial Office, Hotel Pennsylvania, New York, N. Y.

West-Coast Office, Suite 226, Equitable Bldg., Hollywood, Calif.
Entered as second class matter January 15, 1930, at the Post Office at Easton,
Pa., under the Act of March 3, 1879. Copyrighted, 1937, by the Society of
Motion Picture Engineers, Inc.

Papers appearing in this Journal may be reprinted, abstracted, or abridged
provided credit is given to the Journal of the Society of Motion Picture Engineers
and to the author, or authors, of the papers in question. Exact reference as to
the volume, number, and page of the Journal must be given. The Society is
not responsible for statements made by authors.

OFFICERS OF THE SOCIETY

President: S. K. WOLF, 100 E. 42nd St., New York, N. Y.
Past-President: H. G. TASKER, Universal City, Calif.

Executive Vice-President, G. F. RACKETT, 823 N. Seward St., Hollywood, Calif.
Engineering Vice-President: L. A. JONES, Kodak Park, Rochester, N. Y.
Editorial Vice-President: J. I. CRABTREE, Kodak Park, Rochester, N. Y.
Financial Vice-President: O. M. GLUNT, 180 Varick St., New York, N. Y.
Convention Vice-President: W. C. KUNZMANN, Box 6087, Cleveland, Ohio.
Secretary: J. FRANK, JR., 90 Gold St., New York, N. Y.
Treasurer: L. W. DAVEE, 250 W. 57th St., New York, N. Y.

GOVERNORS

M. C. BATSEL, Front and Market Sts., Camden, N. J.

A. S. DICKINSON, 28 W. 44th St., New York, N. Y.

G. FRIEDL, JR., 25 Hunter Ave., Fanwood, N. J.

A. N. GOLDSMITH, 444 Madison Ave., New York, N. Y.

H. GRIFFIN, 90 Gold St., New York, N. Y.

A. C. HARDY, Massachusetts Institute of Technology, Cambridge, Mass.

K. F. MORGAN, 7046 Hollywood Blvd., Los Angeles, Calif.

C. H. STONE, 205 W. Wacker Drive. Chicago, 111.

PROCEEDINGS OF THE SEMI-ANNUAL BANQUET

OF THE

SOCIETY OF MOTION PICTURE ENGINEERS

HOTEL PENNSYLVANIA
NEW YORK, N. Y.

OCTOBER, 13, 1937

About 250 members and guests of the Society assembled at the Fall,
1937, Semi-Annual Banquet held at the Hotel Pennsylvania, New
York, N. Y. Guests at the speakers' table included Mr. C. C. Petti-
john, General Counsel of Motion Picture Producers and Distributors
of America, Inc. ; Mr. A. Demaria, President of Confederation Gen-
erale Cinematographic Fran-aise; Mr. F. Doublier, who has been
identified with the motion picture industry as far back as 1894, when
he worked with the Lumiere firm in France; Mr. H. C. Govil, repre-
sentative of the Motion Picture Society of India; Mr. J. I. Crabtree,
Editorial Vice- President of the Society; and Dr. A. N. Goldsmith,
member of the Board. President S. K. Wolf acted as toastmaster for
the evening.

The Pacific Coast Section of the Society was represented by Mr.
G. F. Rackett, Past-Chairman of the Pacific Coast Section, and Ex-
ecutive Vice- President of the Society.

After making sincere acknowledgment of the cooperation of the
many persons and firms that had contributed to the success of the
Convention (whose names have been listed in the November issue of
the JOURNAL), President Wolf introduced Messrs. Doublier, Govil,
Demaria, and Pettijohn, whose remarks follow:

MR. FRANCIS DOUBLIER: Mr. President, Ladies and Gentlemen:
I started in motion pictures with Lumie"re forty-three years ago, in
1894, turning the crank for them. Monsieur Marriett told me, when
I was given a camera: "Francis, be very careful now. Go out and do
your shooting, but let no one look inside the camera."

So I travelled all over Europe and Asia for five years with that

577

578 PROCEEDINGS OF SEMI- ANNUAL BANQUET [j. S. M. P. E.

camera. It was six inches wide and weighed eight pounds. I
printed the pictures in the hotels where I stopped, and showed them
at night. The local theaters were stores. To prevent anybody's
looking inside the camera I slept with the camera and ate with the
camera.

In 1896 I photographed the Coronation of the Czar in Moscow.
From Russia I went to Roumania, Sweden, Norway, Germany, Japan,
and China. After five years I returned to France, whence I was sent
to America to establish a plant. I am still here, and I hope to be for a
long time.

MR. HARI G. GOVIL : Mr. President, Ladies and Gentlemen : I am
happy to be here and to greet you all on behalf of the Motion Picture
Society of India. The motion picture industry in India is very young,
having started in 1913 with silent pictures, and it was not until 1930
that the talkies were taken up. However, during the past six years
the motion picture business has made tremendous progress in India,
and, although the miscellaneous facts that I shall give you may seem
rather odd when placed side by side, they may assist in giving you a
brief idea of the Indian industry.

Today there are in India nearly 160 motion picture producing com-
panies. A featured picture is produced almost every day of the year.
There are nearly 800 theaters equipped for sound. India is the larg-
est consumer of raw film in the world, outside of the United States.
It may seem rather strange that a country having only 800 theaters
uses such enormous footage of film, but the reasons are that a great
deal of footage is spoiled and the length of feature films is from 14,000
to 20,000 feet.

As in America, the Indians like music very much, and especially
like to listen to their own singers and their own songs. Sometimes
the songs last for fifteen minutes, so it can be understood how much
film is consumed in producing.

I think that this will give you some idea of the motion picture in-
dustry in India, and I am sure that as a result of the technic that
America and the West have developed, we shall not very long lag far
behind.

MR. A. DEMARIA : Mr. President, Ladies and Gentlemen : I am very
pleased to be with you, and I drink to the success of American motion
pictures and to the prosperity of the Society of Motion Picture Engi-
neers.

Dec., 1937] PROCEEDINGS OF SEMI-ANNUAL BANQUET 579

MR. C. C. PETTIJOHN: Mr. Chairman, Distinguished Guests,
Ladies and Gentlemen: We are living in a peculiar world today.
Men who create and conserve are not only carrying the load, but are
paying the bills, and in many instances getting the least consideration
financially out of it with which to pay the freight. When I stop and
think of the things that have been created in this business that has
been so good to so many people, I wonder why the creators have got
so little out of them.

I refer particularly to the group to which you gentlemen belong.
I wonder how many people in our business ever stop to think what
makes this big, fine, interesting, paying business what it is.

We are living in a day of blocs : we have the farm bloc, the labor
bloc, the studio bloc, the actors' bloc, and numberless other guilds and
societies that are all out for themselves. They look at their own tree
and don't look at the forest. If I were to pay you a compliment, I
would say you are the most unselfish group in the motion picture indus-
try, the most modest, and the farthest behind the times in doing
something for yourselves. That is friendly criticism.

I still think that motion pictures are in their infancy. I understand
that you have developed a new device so you can now tell whether a
sound comes from off-stage right or hft. That's something new. If
we stand still in this business, we are hurt. We have to have some-
thing new. We have to keep creating, and you fellows are the ones
who do much of it.

At Budapest this Society accomplished the standardization of
16-mm. sound-films with 20 nations, which means world-wide stand-
ardization. I wonder how many people in the picture business know
what that means. Where would we be if we had different sprockets,
different apertures, and different this, different that. It would be a
chaotic business. Yet you people are responsible for all that
standardization.

The next thing I would like to touch on is this great "undeveloped
field" that everybody speaks of. It is the great field that some call
the "educational field," some the "religious field," and what not. The
motion picture business today is an amusement business, and as far
as theaters are concerned that is what it should stay. When pictures
are used for education, they should be "pedagogic" pictures, and if
for religion, they should be religious pictures. Churches and minis-
ters are in the business of religion ; teachers are in the business of edu-
cation. We are in the business of furnishing amusement.

580 PROCEEDINGS OF SEMI-ANNUAL BANQUET [J. S. M. P. E.

We all have our illusions of people and subjects. I lived fifteen and
one-half years with an illusion undestroyed, working alongside a fel-
low named Will Hays. I don't know why. He is a Republican, and
I am a Democrat. We have few characteristics in common, yet year
after year my illusion of the man is not destroyed. He has grown
with me. And I sometimes think if there could be that understand-
ing between more men — you don't have to think alike, you don't have
to be alike to understand each other — if that could permeate the in-
dustry, all of us would understand the men who create the things with
which we work. Some don't know where these things come from.
This business must go on and on to greater heights, and without you
men, it can't.

May I wish for you tonight simply this, that within the near future
the responsible factors in the business, which you have done so much
to build and which you must keep alive, may know you and under-
stand you and appreciate you more and more?

PRESIDENT WOLF : Annually the Society honors two of its members
with awards. One award is known as the Journal Award, which rep-
resents the most outstanding original publication in the Society's
JOURNAL. Tonight we have the honor of presenting this award.
The award citation is to be given tonight by Mr. E. A. Williford.

CITATION ON THE WORK OF DEAN BREWSTER JUDD
E. A. WILLIFORD

Each year the Journal Award Committee of the Society of Motion
Picture Engineers faces the task of selecting from the issues of the
JOURNAL of the preceding year, the most outstanding paper published
during that period. In addition the Society is required to select a
number of papers, not exceeding five, to be given Honorable Mention.

Because of the high caliber of the papers published in the Society's
JOURNAL, the task of making these selections is a very difficult one,
even though combined with our interest in reading all these papers.
To find the one that stands out above all the other fine papers im-
poses a burden on your Committee that they have sought to dis-
charge with the best of their several abilities.

For the year 1936, the Committee has selected as the recipient of
the Journal Award, Dr. Dean Brewster Judd, of the National Bureau

Dec., 1937 J PROCEEDINGS OF SEMI- ANNUAL BANQUET

581

of Standards, Washington, D. C., for his paper entitled "Color Blind-
ness and Anomalies of Vision" published in the June issue of the JOUR-
NAL. To the uninitiated it will probably be astounding to learn that
it is estimated that about 5 per cent of our total population have color
abnormalities of various types and degrees that are sufficiently im-
portant to disqualify them for many types of work involving color
separation or distinction.

Dr. Judd was born at South Hadley Falls, Massachusetts, in the

DEAN BREWSTER JUDD

year 1900, where he received his secondary education. From the
Ohio State University he received the degree of Bachelor of Arts in
1922, and in 1923 he received his degree as Master of Arts from the
same University. In 1926 he was awarded the degree of Doctor of
Philosophy at Cornell University. In all his higher education Dr.
Judd majored in mathematics and physics. Among the honorary
societies to which Dr. Judd has been elected are Phi Beta Kappa,
Sigma Xi, and Pi Nu Epsilon.

582 PROCEEDINGS OF SEMI- ANNUAL BANQUET [J. S. M. P. E.

After receiving his Master of Arts from the Ohio State University
in 1923, Dr. Judd served as instructor in psychology at the Ohio Wes-
leyan University, later as Research Associate of the Munsell Research
Laboratory at the National Bureau of Standards, as Associate Physi-
cist of the National Bureau of Standards, and since 1937 he has served
as Senior Physicist at the National Bureau of Standards. He is
widely connected with scholastic and scientific organizations, and in
addition to those already mentioned, he is a member of the Committee
on Colorimetry, and Delegate to the Inter-Society Color Council,
Vice-Chairman of the Inter-Society Color Council, 1936-1937, and
with Dr. L. A. Jones of our Society, was the United States representa-
tive in colorimetry on the International Commission on Illumination
from 1929-1935.

Dr. Judd has published about 30 scientific papers in the Journal
of the Optical Society of America, Journal of Research of the National
Bureau of Standards, American Journal of Psychology, Journal of Ex-
perimental Psychology, the Paper Trade Journal, and JOURNAL of the
Society of Motion Picture Engineers.

In 1935 the Papers Committee of our Society communicated with
Dr. Briggs, Director of the National Bureau of Standards, Washington,
D. C., suggesting to him that the subject of color blindness and anoma-
lies of vision was a very important one to the motion picture industry,
and requested that someone on the staff of the Bureau be requested
to prepare a paper on the subject. Because of Dr. Judd's wide ac-
quaintance in this field he was asked to prepare this paper. For the
past ten years Dr. Judd has been in charge of the administration of
tests for color-blindness at the National Bureau of Standards, and dur-
ing that time has become widely acquainted with the literature in the
field of color-blindness and theory of vision.

Mr. Chairman, Mr. President, it is with great pleasure that I intro-
duce to you and to all members of our Society, Dr. Dean Brewster
Judd, Senior Physicist in Optics of the National Bureau of Standards,
as recipient of the 1936 Journal Award.

After receiving the Journal Award certificate from President Wolf,
Dr. Judd responded as follows :

DR. D. B. JUDD: Ever since I had the pleasure of speaking to many
of you two years ago in Washington, I have had a warm place in my
heart for you, because so many of you were kind enough to laugh at
my jokes. I am afraid if I speak very long, you will discover how

Dec., 1937] PROCEEDINGS OF SEMI- ANNUAL BANQUET 583

little I deserve the kind words with which your Chairman of the Jour-
nal Award Committee has described me. But I do want to say I ap-
preciate the honor. It is true that I have published about thirty
papers, and this is the first time I have had concrete evidence that any
of them had been read except by an editorial committee.

MR. WILLIFORD : In addition to the paper chosen by the Committee
for the Journal Award, the following excellent papers have been se-
lected for honorable mention :

"Improved Resolution in Sound Recording and Printing by the
Use of Ultraviolet Light," by Mr. G. L. Dimmick.

"Continuous Photographic Processing," by Mr. H. D. Hineline.

PRESIDENT WOLF : The highest award that the Society can offer to
its members is known as the Progress Medal. This award goes to the
person selected by the Committee who has contributed most to the
science and art of our industry. We have the pleasure tonight to pre-
sent to you Mr. E. W. Engstrom, who will read the citation for the re-
cipient of the Progress Award Medal.

CITATION ON THE WORK OF EDWARD WASHBURN KELLOGG

E. W. ENGSTROM

I am indeed privileged this evening to tell you of some of the ac-
complishments of Edward Washburn Kellogg, who is about to receive
the Progress Award of the Society "for outstanding achievement in
motion picture technology." I particularly consider it an honor to
tell you about Mr. Kellogg's work, since the impact of his work upon
the sound motion picture art is so well known. Just a year ago, Dr.
Goldsmith gave to the Society an account of some of the outstanding
and varied developments in which Mr. Kellogg has played a leading
part. * It is therefore unnecessary for me to attempt in this review a
detailed account of his career. I shall not repeat or attempt to im-
prove upon that citation — the present occasion will be better served
by a more detailed account of one line of effort that Mr. Kellogg
himself would consider his greatest individual contribution to the
motion picture art.

* J. Soc. Mot. Pict. Eng., XXVII (Dec., 1936), No. 6, p. 620.

584 PROCEEDINGS OF SEMI-ANNUAL BANQUET [J. S. M. p. E.

From the time of his first professional interest in motion pictures,
when the General Electric Company first undertook the development
of commercial sound recording on film, Mr. Kellogg has been a cru-
sader for speed constancy. At that time the effects of film speed fluc-
tuations were not generally recognized, nor were the causes of such
fluctuations any better understood. With remarkable vision and
perseverance, he early recognized cause and effect, and set out to build

EDWARD WASHBURN KELLOGG

better mechanisms. In this pioneer work to achieve greater speed
constancy, he employed such features as the magnetic drive, a flexibly
mounted idler, an extra sprocket for isolating the magazine, a double-
roller arrangement to increase the flexibility of the film loop, and two
pressure rollers, one overdriven through a slipping clutch in order to
keep the film snug against the drum. A number of these features
have since become standard in film recording and reproducing equip-
ment, and have found use in commercial designs.

Dec., 1937J PROCEEDINGS OF SEMI-ANNUAL BANQUET 585

Mr. Kellogg recognized that the success of the magnetic drive was
due not only to its effective damping of a flywheel-controlled drum
but also to the fact that the tension on the film loops was relieved,
thereby greatly increasing their flexibility. To take full advantage
of the latter effect, he investigated the properties of loops of various
shapes and studied the conditions for film stability. This work led to
the design of the Photophone PR-4 recorder, and was described in
considerable detail in a paper by Mr. Kellogg, entitled "A New Re-
corder for Variable-Area Recording," published in the JOURNAL of the
Society for November, 1930.

Half the battle to control a fault is accomplished when one can
measure the fault objectively. Mr. Kellogg's work on this aspect of
the fight against speed fluctuations has also been outstanding. He
has been appreciative not only of the value of objective measurements
but also of the need for and difficulty in subjective interpretations of
them. Under his direction, as a consequence, equipment and tech-
nics for the measurement and evaluation of speed fluctuations appli-
cable to both film and disk recording have been developed that
are essentially practical and have found widespread use. This
work has been described in a joint paper by Mr. Kellogg and Mr.
A. R. Morgan, entitled "Measurement of Speed Fluctuations in Sound
Recording and Reproducing Equipment," published in the Journal
of the Acoustical Society of America in April, 1936.

Mr. Kellogg has directed the developments that have to a large ex-
tent resulted in the sound picture recording and reproducing systems
manufactured by RCA. He has directed the development of many
of the important elements, such as optical systems, printers, and
studies of film resolution. He has made valuable contributions in the
field of acoustics and was one of the two men who jointly developed
the dynamic cone type of loud speaker in its present form. He has
been successful in training a group of engineers working with him to
approach their problems with an open-minded attitude and to appre-
ciate the value of careful analysis and investigation.

It is fitting now that something be said of Mr. Kellogg's character
and personality, of those qualities that have caused him to be re-
garded as an outstanding engineer and above all else, and by all
who have known him, as a friend. As one who has had the privilege
of working with him, and who has felt the warmth of his friendship,
it is fitting that I say these things, to honor Mr. Kellogg.

Mr. Kellogg has an uncanny ability to analyze a problem or situa-

586 PROCEEDINGS OF SEMI-ANNUAL BANQUET [J. S. M. P. E.

tion and to separate essentials from details. Following analysis, his
ingenious mind is quick to provide many suggestions for action. As
a result, his associates are eager to discuss their work with him, and
he is always ready to listen. Furthermore, they know that he will
not attempt to take credit for results that should be theirs. In fact,
one more eager than Mr. Kellogg to give credit to others could scarcely
be found. His modesty is as outstanding as his ability, yet no one
could be a stronger advocate of his own convictions.

As a result of these qualities, the relations between Mr. Kellogg and
his associates are always on a high plane of mutual cooperation, es-
teem, and friendship, and these are conditions that lead to accom-
plishment. It is not without significance that one-third of Mr. Kel-
logg's publications are joint papers, a fact that indicates his ability in
collaboration of the most productive sort.

The titles of Mr. Kellogg's published papers speak eloquently of
the wide variety of subjects that have engaged his attention. Still
other subjects that he has investigated might be mentioned, how-
ever, such as stereosonic sound, stereoscopic motion pictures, and
color photography.

Mr. Kellogg has a delightful home. His wife is a true and loving
companion, and they have three growing daughters. The family are
active in community affairs, and are esteemed by their neighbors.

All these things are significant in the character of the man we honor
— student, teacher, scientist, engineer, citizen, and friend.

At the conclusion of Mr. Engstrom's citation, the Progress Medal
of the Society for 1937 was presented to Mr. Kellogg by President
Wolf, and Mr. Kellogg responded as follows :

MR. E. W. KELLOGG: Mr. President, Honored Guests, Ladies and
Gentlemen, and Friends : The kind things that Mr. Engstrom has said
are most gratifying, but coming from the man I know Mr. Engstrom
to be, they are doubly appreciated.

Mr. Pettijohn's remarks about the compensation we engineers re-
ceive for our work, seem almost an invitation for me to speak of the
rewards that come to us. We are no more above financial considera-
tions than others, but perhaps the non-monetary satisfactions that
come, at least to the more fortunate of us, are not fully realized. Our
work is to us what music is to the musician. The musician's great
need is to own his instrument. The artist needs to sell enough paint-

Dec., 1937] PROCEEDINGS OF SEMI- ANNUAL BANQUET 587

ings to buy more paint. So with us it is a great privilege to be given
an opportunity to work on our favorite projects. There are too
many to whom that privilege has been denied, and those of us
who have had such unusual opportunities as I have had, are in-
deed fortunate. If we can see the fruits of our work put to use, and
embodied in things that have important or widespread application,
we have another source of satisfaction that can not be measured.
And then if recognition of our work comes, particularly recognition
such as you have given me tonight, what more could one ask P I as-
sure you that this award is a priceless treasure to me and to my family,
a treasure that no tax collector or bankruptcy proceedings can take
away. World renown is something that there isn't enough of to go
around so we can all have some, but the esteem of friends is far more
valuable, and we can all have it if we earn it. Special recognition by
this Society goes far in the direction of national and foreign notice,
but the best part of it is that it is a token from those whom I have had
the pleasure of knowing as friends.

Attendance at many conventions has convinced me that the follow-
ing definition is a good one: "A convention is a gathering of people,
each of whom is willing to listen to speeches by others, for the sake of
having an audience when it comes his turn." Just now, through your
courtesy, it seems to be my turn, and I wish to take the opportunity
for some comments on the subject of progress, and of research labora-
tories.

The value of technical progress is being widely questioned today,
and probably rightly so. Widespread unemployment has stimulated
such inquiries. In our own field what we hope is that better sound
recording will mean more music, not fewer musicians — more and bet-
ter music, in our homes, and in our places of recreation. But the
question has many aspects besides that of unemployment.

The sound motion picture is unquestionably one of the most power-
ful means for making an impression upon the human mind that has
ever been evolved, and the more perfect it is made, the more potent
it becomes. Is its influence for good or for ill? When I was studying
civil engineering I became much interested in the principles of sewage
disposal, and for two years I followed that line of work. It does not
sound like a noble calling, but you must admit the elimination of a
stench is a service to humanity. I must confess that there have been
times when I felt that some way ought to be found to apply the prin-
ciples of sewage disposal to motion pictures.

588 PROCEEDINGS OF SEMI-ANNUAL BANQUET [J. S. M. P E.

The great American philosopher, Mark Twain, has remarked that
fleas are good for a dog. We all of us need our fleas from time to time.
The boycott, started by the Catholic Church, and followed up by
others, probably served as a swarm of fleas to the motion picture in-
dustry. Whatever may have been the cause, there has been a change
that to many of us has been most gratifying, and I think we may feel
profound gratitude for the position taken by our critics. It has
seemed to me, that it was about that time someone discovered that it
is not necessary to portray all the characters in a story as self-indul-
gent degenerates in order to make them interesting. In his address
last Monday at the Society's luncheon, Mr. Quigley made some very
interesting remarks in justification of what has been called "the Cin-
derella type of story," and condemning the mistaken point of view of
people, who in the name of "realism," portray only the seamy side of
life. I would go a step farther and say that such "realists" are the
worst of liars. You and I know that the world is full of honest, whole-
some, lovable people, who want to do the square thing, and although
they may not talk much about it, they have their ideals. Actually
the human race isn't so bad — it comprises many of the best people in
the world.

The effects of better motion pictures, whether for good or for ill,
depend upon the use that is made of them. We must have enough
faith in our brother and sister human beings to believe that in the long
run they will make the right kind of use of the agencies that are put at
their disposal.

It is only proper that we technical men should express our recogni-
tion of the fact that contributions to progress take many forms, and
that while the working out of purely technical problems is an essential
part, there are other equally important r61es. Directors and manag-
ers who express their faith in the future make progress possible by ap-
propriating liberal sums to research, and by backing their men through
periods of little apparent accomplishment. Managing engineers and
other executives who see that emphasis is placed upon the most valu-
able projects, and who can keep enthusiasm alive in their organiza-
tions, engineers who put developments into commercial shape, sales-
men who push the best things, workers in the field who find the best
ways of using things and give us the benefit of their experience — all
these, in addition to originating many of the most valuable ideas, play
an indispensable part in furnishing the public with something better
than it had before. We men who work in advance-development and

Dec., 1937] PROCEEDINGS OF SEMI- ANNUAL BANQUET 589

research laboratories have an unfair advantage in being given credit
for advances. What we have done is on record, in models, patents,
and papers. The part played by other members of the big team is
mostly unwritten history — just part of the day's work.

There are a few misconceptions about laboratories. I believe that in
the minds of many the ideal research laboratory is a cloistered place
where people with impressive arrays of advanced university degrees,
bury themselves for months on end in profound problems that have
only a remote bearing on our everyday lives. As part of the same pic-
ture, it is often thought that to do our best work, we should be left alone
for long periods, to work out problems. There are no doubt in-
stances where that should be done, and there are persons who can
work best that way, but most of us do more thinking when there are
plenty of urgent problems confronting us. There are few things that
are so gratifying as seeing our developments put to use and there is
great zest in a job when we are "sold short."

There is another idea that we often run across. When a man has
failed to make good in other capacities, the suggestion is made that
he "would probably be all right for research." Of course we don't
relish this, but it is probably a reflection of the idea that a research
man does not have to be highly practical, rather than that he doesn't
need to have any brains. It is true that lively imaginations are
needed for advanced development, and we may forgive some over-en-
thusiasm. There are plenty of people to hold the enthusiast down.
It is also true that a mistake is much less expensive in the development
laboratory than it is likely to be elsewhere. So we don't demand of a
research man that he shall not show occasional stupidity. All we ask
is that once in a while he have a bright idea. Nevertheless a good per-
spective is most valuable. I do not believe there ever were more thor-
oughly practical men than some of the leaders in research whom it has
been my good fortune to know. I went to the General Electric Re-
search Laboratory during the War, full of ideas of increasing the sensi-
tiveness of microphones for submarine detection. I found that Dr.
Coolidge was getting remarkable results with a pair of hollow rubber
balls on the ends of brass pipes. One of my earliest recollections of
Dr. Langmuir was of his standing in the hallway talking to a group
of men and giving a vivid description of the treatment the listening
gear would get as it was heaved over the side of the ship. A day or
so later I encountered Chester Rice investigating microphones with a
club, to estimate their ability to withstand depth bombs.

590 PROCEEDINGS OF SEMI-ANNUAL BANQUET [J. S. M. P. E.

When Rice and I were working together, we would sometimes find
after putting in a lot of work on a project, that it was covered by some
old patent. On one such occasion his remark was, "Kellogg, the
ancients have stolen our inventions." Now although I resent such
mean tricks on their part, I have conceived a great admiration for
"the ancients." We have seen so many impressive developments in
the past few years that we sometimes belittle the accomplishments of
our predecessors. When I reflect on the limited facilities that were
at the disposal of the great pioneers, and the fact that they did their
work for the most part singly and without the stimulus of numerous
associates to exchange ideas and experience, I marvel at their accom-
plishments. Rayleigh's Theory of Sound, published in 1877, has been,
as many of you know, a veritable Bible to sound engineers. At the or-
ganization meeting of the Acoustical Society I made the remark that
if we worked hard and pulled together and lived long, we might get a
good start toward catching up to Rayleigh. A few years ago in con-
nection with a patent suit, there were uncovered in the Smithsonian
Museum some photographic sound recordings made by Alexander
Graham Bell and Sumner Tainter. They were on big glass disks.
We had some photographic copies made and rigged up a machine for
playing them. Although, to be sure, we could distinguish only occa-
sional words, there was indeed a thrill in reviving these voices of more
than fifty years ago. The making of these recordings is described in
U. S. Patent No. 341,213, filed in 1885 (and the voice on the record also
gives the date). One curious method of recording is described. The
exposing light-beam passed through a glass plate, against which they
caused a tiny jet of ink to play. The nozzle was attached to a dia-
phragm which caused it to vibrate and produce waves of ink running
down the plate, obscuring more or less of the light. I am not sure of
the exact method by which the records were made, but they were
variable-density records, and although I am not in a position to speak
with authority, I strongly suspect that the precedent established by
Bell at that time was a determining factor in the subsequent choice of
that type of record by his successors. But imagine the delight of
myself and my RCA friends to find the following in the patent. Alex-
ander Graham Bell invented the light-valve: He describes an arrange-
ment that functioned optically exactly as does the present valve.
Then he states, "The recording apparatus may be as shown in Figs. 1
and 2. The edge of the vibrating style being parallel with the length
of the slit and consequently parallel with the radius of the tablet (or

Dec., 1937] PROCEEDINGS OF SEMI-ANNUAL BANQUET 591

disk) through the image thereon, the record will be of practically uni-
form width, but variable in shade, depth, or intensity. The effect,
it will be observed, is here produced not by varying the intensity of
the image, as in the apparatus of Figs. 1 and 2, but by the less perfect
mode of varying its size." In other words, Bell anticipated the "rib-
bon velocity distortion" discussed by Shea, Herriott, and Goehner in
the June, 1932, JOURNAL of the Society. Bell then describes a modifi-
cation as follows: "The apparatus of Fig. 9 is the same as that of
Figs. 6, 7, and 8, except that the style vibrates lengthwise of the slit,
increasing and diminishing its length. Consequently the record will be
of varying width. This form of record has certain advantages. It can,
for example, easily be magnified, so that the smallest vibrations be-
come very evident." Thus Bell "stole the thunder" of my 1935 paper.
Unfortunately, Bell's advice on this important subject was not
adopted. Why should such words of wisdom have gone so long un-
heeded?

But to return to the subject of future progress, all of us who want bet-
ter things are a part of the great movement that brings them. So
let's keep on, and we won't be satisfied until sound and picture repro-
duction are so perfect that when the heroine on the screen sneezes,
everyone in the front seats will come down with a cold in the head.

PROPAGANDA, EDUCATION, AND THE ENTERTAINMENT

FILM

MARTIN QUIGLEY*

An address presented at the Luncheon of the Society on the opening day (October
llth) of the Fall, 1937, Convention, at the Hotel Pennsylvania, New York, N. Y.

The present degree of technical perfection enjoyed by the motion
picture medium of expression is an emphatic testimonial to the skill
and accomplishments of the members of the Society of Motion Picture
Engineers.

To your membership, who have contributed so importantly to mak-
ing the motion picture the effective medium that it is today, a discus-
sion of some general policies affecting the entertainment film may be
of interest.

I approach with some reluctance this discussion before your Soci-
ety, knowing as I do of your absorbing interest in the technological
aspects of the motion picture. But it seems to me that where there is
an interest so great, and an accomplishment so great, in these many
technical matters there may well be presumed an interest in how the
finished medium is being employed, and why.

There is also to be presumed, I imagine, an interest in any plans and
pressures calculated to introduce the film into a new and different
function in modern life.

It is to many a singular fact that the film thus far in its career has
been addressed almost exclusively to the objective of entertainment.
It has so happened that the film and its processes have thus far been
employed almost exclusively in the business of entertainment by an
industry that has grown great out of the opportunities presented by
the medium. I do not say that this is as it should be. I say only
that this is as it is.

It so happens that there are now many persons of standing and in-
fluence who have become poignantly discontented with this state of
affairs. Their discontent has resulted in certain emphatic declara-
tions that, from this point on, the amusement industry should cease

* Quigley Publishing Co.. New York, N. Y.
592

ENTERTAINMENT FILM 593

to be exclusively an entertainment industry and, rather, should em-
bark upon the provinces of education and propaganda.

Although the processes of motion picture production and exhibi-
tion are readily available to all who may have requisite financial re-
sources, it does not satisfy these discontents to point this fact out to
them. Rather, it results only in their insistence that the entertain-
ment industry should embark upon these provinces which to it are
strange and foreign.

There is, I fear, among at least some of those who would pressure
the entertainment industry into projects of propaganda and educa-
tion, a certain lack of candor. They say that the entertainment film
is, in fact, an educational activity. If this assertion were accepted, it
might seem that they would have nothing further to argue about.
That, unfortunately, is not the case. Their argument about the en-
tertainment film's being an educational activity is, to my mind,
something in the way of a come-on.

This because it certainly would be argued that if the entertainment
film is, indeed, an educational and propaganda activity then these
educationalists and propagandists should have a voice in determining
what is produced and how it is produced.

There may be some fine academic hairs to be split in determining
just what is education and just what is entertainment. But for all
practical purposes it seems to me that the answer is clear. There is a
great difference between the generally educative influence of a motion
picture and those definite measures of education that are the business
of the educational institution.

It is undoubtedly true that the motion picture, indirectly, is an
educative force. In virtually the same sense almost all vital ex-
periences of life are educative. But there is a vast difference between
presenting a dramatic story in motion picture form, which may in-
cidentally convey information and create temporary or enduring
mental pictures, as compared with the pedagogical exposition of
a subject.

The crux of the question, of course, is not in the acceptance of the
idea that the entertainment film has an educative influence. Rather,
it is in the acceptance of the idea that the objective of the entertain-
ment picture is education. Any encouragement to this latter idea
inevitably would lead to a destruction of the present popularity of the
screen and the enslavement of the medium in the hands of fadists and
fanatics.

594 M. QUIGLEY [J. S. M. P. E.

I, of course, voice no denial that the motion picture is an influence,
and a great influence, upon the public mind. Unquestionably, it sug-
gests patterns of thoughts and confirms habits of thinking. It is a
tremendous force of modern life in its influence upon conduct and be-
havior.

It is one thing, however, when these results are incidental to the
telling of a dramatic story for dramatic purposes. Quite another
thing is to set out deliberately to inculcate ideas and habits of thought.

Among the current assailants of the industry's policy there are those
who condemn the motion picture for not presenting what they assert
to be truth and reality. Now, this is what I believe they mean :

First, when they speak of truth they mean their own individual in-
terpretation of what is true — not what may be your interpretation,
or mine, or the producer of the particular picture. When they say
they want reality they mean they want presented certain facts of life,
the drumming of which into the public mind is calculated to prepare
the public mind for particular ideas of social, political, and economic
reform.

I do not absolve the motion picture of any of its proper responsibili-
ties. Rather, I fix upon it certain heavy and, to my mind, vastly
important responsibilities. I hold that the entertainment film has an
unqualified right to address itself singly to the objective of entertain-
ment. I hold, however, that in serving this objective it must avoid
anything, and everything, that tends to lower the moral standards of
its audiences, or to invade public order and welfare.

Viewed in certain of its aspects, this situation, I believe, strikes
close to certain of the most formidable trends of modern life.

The screen is regarded covetously by those who seek to alter radi-
cally our social and economic system.

It is an interesting fact that the pictures that seem to please most
these objectors against industry policy are films of a realistic charac-
ter— and the more bitter the realism the more acceptable they are.

This attitude is explainable, I believe, on the grounds that those
who seek a revolution seek as a means to that end the fostering of
those things that create public discontent and dissatisfaction.

Recently, at a public discussion, one person who is busily engaged
upon remaking the world and its people to his own measure deplored
what he calls the "Cinderella" motif in motion pictures.

He seems to resent the hours of happiness and contentment that the
motion picture theater affords to millions of persons the world over.

Dec., 1937] ENTERTAINMENT FlLM 595

Rather, I believe, he wants the motion picture theater to contribute,
instead of happiness and contentment, a spirit of discontent and a fer-
vor of reform to its audiences.

Heaven knows that there is much need of reform. But I, for one,
do not want to see the motion picture theater become a place of politi-
cal debate instead of the place of recreation and refreshment that it is.

Behind the attitude that wants bitter realism on the screen is, I be-
lieve, that same spirit that condemns religion as opium of the people.
To those who hold this attitude, the film that offers only recreation
hinders the approach of the revolution.

It seems to me entirely proper that a group of men should have
taken the motion picture medium of expression and built out of it
a great entertainment industry. It further seems entirely proper to
me that, within those limitations necessarily imposed upon entertain-
ment of all kinds in a decent civilization, these men, and the partner-
ships and corporations that are their successors, should be permitted
to go about their business and not be diverted into provinces where
they do not belong.

The entertainment industry holds no exclusive mastery over this
medium of entertainment. Any others who wish to see the medium
put to other uses are at liberty to do so.

This, it seems to me, suggests the only sensible policy for the enter-
tainment industry to follow, and any other course would, I believe,
eventuate in a colossal blunder.

TELEVISION DEMONSTRATION
AT THE FALL CONVENTION

Summary. — Proceedings of the demonstration of television given by the Radio
Corporation of America and the National Broadcasting Company on October 14,
1937, as the final session of the Fall, 1937, Convention of the Society.

The final session of the Fall, 1937, Convention at New York, N. Y.,
consisted of a demonstration of television by the Radio Corporation
of America and the National Broadcasting Company on the evening
of October 14th. The demonstration was held on the 62nd floor
of the RCA Building, where twenty television receivers had been ar-
ranged in a long hall so that groups of ten to fifteen persons could
view the image at each receiver.

In view of the fact that only about 200 persons could be accom-
modated at one time, two identical demonstrations were given at
8 :00 P.M. and 9:15 P.M. The televised performance consisted of both
motion picture film and live entertainment, including two humorous
sketches written for television, harp solos, a piano and xylophone
duet, and a newsreel. Concluding each show an interview between
an Officer of the Society and one of the studio actors was televised.
The participant in the first show was L. W. Davee, Treasurer of the
Society, and in the second show, E. A. Williford, Financial Vice-Presi-
dent elect. The show was picked up by iconoscope cameras in the
NBC Studios on the third floor of the RCA Building in Radio City
and relayed by coaxial cable to the transmitter in the tower of the
Empire State Building, from which point it was broadcast to the re-
ceivers on the 62nd floor of the RCA Building.

Opening the proceedings of the evening Mr. J. I. Crabtree, Edito-
rial Vice-President of the Society, introduced Mr. David Sarnoff,
President of the Radio Corporation of America, who welcomed the
members of the Society and addressed them in the following words :

MR. SARNOFF: It is the policy of the Radio Corporation of
America to keep all who have either a direct or contingent interest in
television, as well as the public press, informed of its progress. We
feel that the members of the Society of Motion Picture Engineers,
who are our guests this evening, have not only an interest in television
596

TELEVISION DEMONSTRATION 597

but also a professional experience that makes them unusually well
qualified to judge its possibilities and comprehend its problems. It
is therefore with particular pleasure that we shall give you this eve-
ning a brief demonstration of our latest developments in this new art.

Television is today an unfinished product. Its progress up to now,
and some of the problems that still remain to be solved, are parallel
in many respects to the early progress and problems of the motion pic-
ture industry. You who remember the flickering images and the
crude scenes of the early films — in contrast to the technical and artis-
tic perfection of present-day motion pictures — can understand what
we are up against in getting television in shape to perform a useful
public service.

We brought television out of the laboratory and "into the open
air" on June 29, 1936. At that time we began transmitting television
images from the RCA experimental station at the top of the Empire
State Tower to receivers in charge of our engineers at selected obser-
vation points throughout the metropolitan area. As a result of con-
tinuous experiments under actual service conditions the transmitting
antenna and much of our other equipment have been remodelled
several times.

Week by week and month by month television engineering progress
has seemed slow and difficult. Yet when we look back today over the
period of only one year and four months that separates us from our
first television field-tests we can observe a number of definite and
promising achievements.

Where a year ago each separate image was scanned with 343 lines,
today we are scanning with 441 lines. This standard of picture-defi-
nition is now generally regarded as satisfactory. During the past
year the color of television pictures has been changed from green to
black-and-white, and their brilliance greatly increased. The size of
the picture has been increased from approximately 5X8 inches to
7 X 10 — almost double the area. In addition, important progress has
been made in projecting television pictures of approximately 3X4
feet upon a screen. You will see tonight our first demonstration of a
broadcast television program projected upon such a screen.

These are some of the technical advances in television accomplished
by RCA engineers during the past twelve months. During this time
the broadcasting service of RCA — the National Broadcasting Com-
pany— has been operating an experimental television studio in the
RCA Building, and has also made significant progress in the develop-

598 TELEVISION DEMONSTRATION . [J. S. M. P. E.

ment of television programs. Lighting and make-up, sound-effects,
scenic design and studio architecture, as well as the manipulation and
coordination of television cameras, have been the subject of continu-
ous study and experiment by NBC engineers and program special-
ists. New technics for the writer, the director, and the actor are be-
ing explored. Practical experiments with outside television pick-up
equipment will get under way within the next few weeks. It has be-
come apparent that the television program, while borrowing much
from the stage, the screen, and sound broadcasting, must blaze many
new trails in order to develop a form of presentation fitted both to the
scope and to limitations of the new medium.

While the technical problems yet confronting us are formidable,
they are not the only obstacles that lie in the path of television's com-
mercial introduction to the public on a general scale. In evolving a
satisfactory program technic we have already learned that television
programs will cost much more money than sound broadcast programs.
If television programs are to be provided through the support of com-
mercial sponsors, advertisers must first be furnished with sufficient cir-
culation to justify their expenditures. Here we have the dual problem
of simultaneously creating a cause and an effect : we must create large
audiences in order to support costly programs, and we must build
costly programs in order to attract large audiences.

To meet the requirements of a nation-wide television service, vast
sums of money must be invested in new facilities. The present range
of useful television signals is less than 50 miles. The creation of even
limited networks, with connection by coaxial cable or radio relay, is a
highly expensive undertaking. As in every other pioneering develop-
ment and rapidly changing art such investments can not be made
without risk. I believe, however, that the same American pioneering
spirit of private enterprise that has given us great systems of transpor-
tation and communication, and has produced the great industries of
the automobile, motion picture, and radio, will likewise provide us
with a nation-wide system of television.

Radio and motion pictures rank at the top of the younger industries
that have furnished extensive employment to both capital and labor.
In television, the newest child of the radio art, we can foresee another
vigorous industry, which will provide many new avenues of employ-
ment and will furnish opportunities to the younger generation looking
for careers in new fields.

•We can, I believe, look forward to the ultimate establishment of an

Dec., 1937] TELEVISION DEMONSTRATION 599

American television system that, like our present system of sound
broadcasting, will employ many thousands of workers, will offer a
unique advertising service to American business, and will render a
free educational and entertainment service -to the public.

Following Mr. Sarnoff 's address, a further description of the techni-
cal arrangements for the demonstration was given by Mr. Robert
Morris of the National Broadcasting Company staff. The RCA tele-

FIG. 1. The television receiver, with its reflecting mirror in the lid of
the cabinet ; and the 3 X 4-foot screen upon which the image was pro-
jected by the projection kinescope shown in Fig. 2.

vision system has previously been described in the JOURNAL by Dr.
V. K. Zworykin1 and R. R. Beal.2 A reproduction of the television re-
ceiver used in the demonstration is shown in Fig. 1. In the receiver
is a kinescope, which consists of an electron gun and a fluorescent
screen assembled within a vacuum tube. The negative electrode of
the tube delivers a stream of electrons varying in intensity with the
strength of the radio signals received. By means of magnetic de-
flection coils, this beam of electrons is made to scan the chemically
treated end of the vacuum tube, 12 inches in diameter, which emits
light when impacted by the electrons. The beam traces a pattern
of 441 lines to the inch, 30 times a second, which pattern is re-

600 TELEVISION DEMONSTRATION [J. S. M. P. E.

fleeted into a mirror in the lid of the receiver. The image viewed
in this mirror is approximately 7 X 10 inches in size. The new tubes
produce black and white images of good definition and intensity,
through the use of a new fluorescent chemical material. Tubes that
were used previously gave images having a greenish hue.

In addition to viewing the images in the reflector of the receiver
shown in Fig. 1, the images were reproduced by a newly developed
projection kinescope, shown in Fig. 2, which projected the image upon
a screen approximately 3X4 feet in size, shown also in Fig. 1 . The
projection kinescope resembles, in general construction, its counter-
part used in delivering images to be viewed directly or as reflected in
the mirror in the top of a console receiver. In the projection type,

FIG. 2. The projection kinescope.

however, the electron beam scans an area of iy2 X 2 inches,
creating on the phosphorescent end of the tube a picture of much
greater brilliancy. The image thus created is then projected through
a lens system without the assistance of any additional light-source.

The great difficulty of developing television projection is to produce
sufficient light in the screened image. For that reason, a new high-
current electron gun for generating an extremely slender electron
beam of great intensity had to be developed (Fig. 2) . The electrons
are passed through three metal focusing disks, each having an aper-
ture about 1 mm. in size. They then pass through a fourth disk hav-
ing an opening too small to admit a human hair. After this the beam
is controlled by deflection coils and made to scan a small area at the
flat end of the tube.

Fig. 3 is a view of the television studio, showing two television
cameras, microphone boom, one set (left background) being televised,

Dec., 1937]

TELEVISION DEMONSTRATION

601

and another set being installed (center background) by the studio as-
sistants. On the ceiling can be seen the ventilating ducts and the in-
candescent lamp units. Very great luminous intensity is required for
television, and at times the lighting load runs as high as 30 kilowatts.
The amount of heat generated as a result of such intense illumination
in such a small studio may be well appreciated, and it would be impos-
sible to conduct performances without a ventilating system of consid-
erable power. The ducts on the ceiling are the outlets. The ex-

FIG. 3. View of the studio, showing the two television cameras televis-
ing a scene in the corner of the studio, while a new set is being prepared
in another corner.

change of air in the studio is so rapid that a very distinct draft can be
felt beneath these ducts.

At the rear of the studio (and not shown in Fig. 3), and elevated
about fifteen feet above the studio floor, is the monitor and control
room, in which are located the controls for the two cameras, as well as
two kinescopes wherein are reproduced the images being televised in
the studio and viewed in the mirrors of the receivers after transmis-
sion.2 In televising a scene, one television camera, containing the
iconoscope, picks up the scene from the desired distance at the de-
sired angle. While this "shot" is being broadcast, the other camera
moves into the position required for the next "shot." At the appro-

602 TELEVISION DEMONSTRATION

priate moment, then, according to the script, the first camera is faded
out and the second faded in. All the while, the microphone operator
follows the usual procedure of picking up the voice. As the cameras
are mounted on trucks of the usual sort, many of the effects produced
in the usual motion picture studio can be achieved, such as moving
shots, panning, close-ups, etc.

For more than a year the National Broadcasting Company has
been engaged in experimental broadcasting of high-definition television
including the projection of television performances transmitted from
the top of the Empire State Building, and observation of the images
received at one hundred selected points in the New York area. The
latest additions to the experimental system include a mobile unit,
shortly to be delivered, for televising outdoor scenes and news events.

The Society is indebted to the Radio Corporation of America and
the National Broadcasting Company and their staffs for staging this
demonstration as a session of the Convention; in particular, thanks
are due to Mr. David Sarnoff, President of RCA; Mr. Ralph R.
Beal, Director of Research of RCA, and to Dr. B. E. Shakelford, Mr.
F. E. Mullen of RCA, and to Mr. Robert Morris of the NBC staff.

REFERENCES

1 ZWORYKIN, V. K.: "Iconoscopes and Kinescopes in Television," J. Soc. Mot.
Pict. Eng., XXVIII (May, 1937), No. 5, p. 473.

2 BEAL, R. R.: "RCA Developments in Television," /. Soc. Mot. Pict. Eng.,
XXIX (Aug., 1937), No. 2, p. 121.

POSSIBILITIES OF STEREOSCOPIC MOTION PICTURES*

G. W. WHEELWRIGHT, 3rd**

Summary. — The historical background of three-dimensional motion pictures is
first discussed, leading up to the requirements of true stereoscopy and a discussion of
some of the factors involved, such as overlap, detail, apparent sizes of objects, haze,
lighting effects, and two-eye pictures taken eye-distance apart. Serious three-di-
mensional work falls into two classes: (a) critical-angle stereoscopy, and (b) anaglyph
stereoscopy. Under the latter heading falls the use of colors to achieve stereoscopic
effects, as in Lumiere's work, and Audioscopics, which have several disadvantages;
also polarizing anaglyphs, first operated by Anderton in 1893, and most recently
through the use of Polaroid.

Advantages to be gained from three-dimensional pictures in color as opposed to
single pictures using the same color system are explained. Some of the problems of
photographers and theaters in using the Polaroid system are described, followed by a
discussion of the advantages of stereoscopic pictures in dramatic delineation.

The subject of stereoscopy is age-old, as we all know. Leonardo da
Vinci in some of his writings indicated that he understood the principle
of two-eye pictures and the geometrical differences between what one
eye saw and what the other eye saw. The original work of making
mechanical devices that would reproduce for us the stereoscopic effect
we should have seen if we had been present was started between 1832
and 1837. There is some discussion whether Mr. Eliot or Professor
Wheatstone did the first work. Certainly, Eliot's suggestions were
that one should hold the pictures in such a manner that one's eyes
were crossed when viewing a pair of pictures, and he showed a mechani-
cal means for preventing each eye from seeing the picture not in-
tended for that eye. It was Wheatstone, however, who did the
excellent thorough-going analysis of stereoscopy.

Another famous man of that period, Sir David Brewster, also gave
considerable time and attention to the subject. Whereas Wheatstone
had held two pictures and viewed them through mirrors so adjusted
that each eye saw only its own picture, Brewster conceived the idea
of using first two lenses and, later, parts of two lenses to make up the

* Presented at the Fall, 1937, Meeting at New York, N. Y.; received October
4, 1937.

** Land-Wheelwright Laboratories, Boston Mass.

603

604 G. W. WHEELWRIGHT (J. S. M. P. E.

familiar device known to us all as the stereoscope. This device em-
ployed two pictures taken eye-distance apart and shown to our eyes
through a box-like device, each eye having its own lens focused upon
its own picture. It was far simpler to use and more practicable for
general use than the Wheatstone viewer. It suffered from the serious
disadvantage in close analytical work that pictures could not be
substantially greater than 2l/2 inches in breadth, which is, roughly,
the normal eye separation of the human being. Our own Oliver
Wendell Holmes later suggested minor improvements employing
Brewster's method of viewing.

Soon after this, stereoscopes enjoyed an enormous popularity; and
every amateur, as well as a host of professional photographers, was
taking stereoscopic pictures. Among the many possible reasons for
the subsequent loss of interest in stereoscopy, two stand out: many
persons, due to ignorance of the subject or the desire to fool the
gullible public, took only one picture of the scene they were making,
duplicated it, and showed it separately to each eye. Although this
duplication creates in the mind of the observer something different
from the ordinary viewing of a single picture, it, of course, does not
give true stereoscopy. The second, and perhaps more important,
reason for the brevity of the stereoscope's popularity, is the fact that
during the observation of the picture the observer completely cuts
himself off from the rest of the world. This is essentially an unsocial
act. When viewing pictures with a party of friends, it is difficult, if
not impossible, for all members of the group to enjoy simultaneously
the reactions that the observer personally is enjoying.

In the case of serious study or consultation by a group of men, such
as doctors viewing x-ray stereograms, these stereoscopes greatly
lengthen the period of examination and consultation ; and often such
observers subsequently do not agree to what they saw individually.
If they had all been able to look simultaneously, they could have
reached a conclusion more rapidly and with less uncertainty.

It would now seem worth while to consider the requirements of
true stereoscopy. The various factors that contribute to the percep-
tion of depth are :

(a) Overlap. In a single picture the branch of a tree, for instance,
cuts across a person's body, thereby showing that the branch must
be in front of the person, while not telling exactly how far in front.

(b) In a single picture, a noticeable concentration of detail in the
foreground and lack of such detail in the background.

Dec., 1937] STEREOSCOPIC MOTION PICTURES 605

(c) In a single picture, the diminution in size of known objects such
as telegraph poles along a roadside running off into the distance.

(d} In a single picture, haze and general blue tone of distant scenes.

(e) In a single picture, lighting effects. It is well known in the art
that depth effects can be greatly enhanced by clever lighting. A
common trick of the expert photographer is to place long shadows in
his picture. Other such devices produce stronger suggestions of depth
than does the amateur's usual flat lighting.

(/) Two pictures taken eye-distance apart and observed in some
manner such that each eye sees its own, and only its own, picture. It
is probably safe to say that no serious attempt at stereoscopy can
hope to be successful unless it takes into account the fact that a
person's visual perceptions of reality depend in part upon the fact
that he receives not one but two sets of impressions of the outside
world. Each of these impressions is in itself clear and distinct, and
has its own geometric perspective differing from that of the other im-
pression because of the distance apart of this hypothetical observer's
eyes. In general, the appearance of the pictures as a reality rather
than as an illusion is probably most satisfactory when the normal
condition of viewing is rigorously observed. It does not follow from
the fact that a separation of 2l/z inches in taking the pictures produces
a result far more pleasing than a single picture that therefore two or
three times normal interocular separation in taking the pictures
would lead to an effect two or three times as pleasing. For photog-
raphers who do not understand in detail the geometry of stereoscopic
photography and viewing, the safe rule is to use normal eye separation
in taking.

Serious work in stereoscopic photography has developed into two
general technics, each of which is based upon the general idea that
each eye must see its own picture and only its own picture.

One general type of device for stereoscopic viewing makes use of
the difference in direction from which the two eyes see the picture.
Ives has given this method of attack much serious thought and has
done the outstanding work in this field. A result has been the parallax
panoramagrams now seen often in drugstore and department store
windows. The device depends for its success upon taking a picture
from a series of positions in an arc around the object and showing
these so shielded by a vertical grid that the observer's right eye sees
a series of vertical strips composing the right-eye picture only and his
left eye sees another series composing only the left-eye picture. Cer-

606 G. W. WHEELWRIGHT [J. S. M. p. E.

tain viewing positions for this type of work are unsuitable, and taking
the pictures is difficult. Registration of the strips in such a pattern
must be extremely accurate, and it is difficult to get the required de-
tail for each picture. All these considerations militate against its
ever being of broad commercial usefulness. Objects can be photo-
graphed in the laboratory and shown there, however, and the results
stand as a testimonial to Ives's careful work and to his ingenuity.

The second general technic of stereoscopic reproduction involves
the use of filters so chosen that with a stereoscopic pair of pictures
made visible respectively in two kinds of light, each eye sees only the
picture intended for it. This method divides into the use of comple-
mentary colors and the use of polarization. Using red and green
glasses, Norling and Leventhal have produced the extremely enter-
taining series of pictures known to the public as "audioscopics." In
France, Lumiere, of color-plate fame, utilized two colors, in his case
yellow and blue, to produce stereoscopy in motion pictures. It seems
that the possibilities of this type of showing have been pretty thor-
oughly exploited. The disadvantages are three: (1) When two
colors are used to produce stereoscopy, there is bound to be retinal
rivalry between the eyes, especially in viewing large, clear areas such
as of the sky or water; and it is doubtful whether long presentations
(that, is longer than ten or fifteen minutes) can be watched by a nor-
mal audience without some eye-strain. (2) Many authorities, of
whom Troland is one, say that such anaglyphs produce special separa-
tions suggesting the flats in stage scenery. They do not produce
rotundity or solidity; that is, the niceties of stereoscopic sensation
seem to be absent. (3) Such a use of color to produce stereoscopy
precludes the use of varied color in the pictures themselves to en-
hance the suggestion of reality.

With the method depending upon polarization, work was done by
Anderton as far back as 1893. Using piles of glass plates, he showed
that three-dimensional pictures obtained by this method were a
laboratory possibility; but his necessary use of glass plates made
them economically and practically an impossibility.

With the advent of Polaroid, l the thin polarizing sheeting that can
economically be produced in large areas, there has been a new in-
terest in the field. Professor Kennedy of Smith College, at the re-
quest of the Carnegie Corporation, has been for the past two years
studying its use in the serious study of sculpture and art in general.2
Among others working in the field at present are Professor Roulon

Dec., 1937] STEREOSCOPIC MOTION PICTURES 607

at Harvard and Professor Rule at the Massachusetts Institute of
Technology.

The present is an auspicious time to consider the motion picture
field and the subject of stereoscopic motion pictures. Color movies
are today better than ever before and show promise of still greater
improvement. Polaroid is now available, and this permits for the
first time color movies in three dimensions. There is considerable
laboratory evidence to indicate that the ordinary run of color-film,
when stereoscopic, is considerably more effective than the best single-
eye color pictures. Kennedy2 points out several good reasons: (7)
In nature the respective highlights are in slightly different positions
for the two eyes. This is part of our natural impression of the world.
(2) An effect is produced upon any object by the kind of light illumi-
nating the object. To give an example, suppose we have a statue of
pink or black marble in a room in which the color is predominantly
green. In such a case, one will have not white reflections, but green
reflections. Now this experience is common, and our eyes are able
to remove, as it were, the green reflections from the pink marble and
see the marble as it really is, whereas one is unable to do so with a
single picture of such a pink marble statue on which there is a green
reflection. This is a good experimental reason why, no matter how
good color reproduction may become, there will always be dissatis-
faction in the representation of colored objects by non-stereoscopic
"flat" movies. All objects have to be illuminated, and from all
surfaces there is more or less reflection of such illumination. Gold
and luminous objects generally have been the despair of color
photographers. This again is partly due to the fact that these are
essentially two-eye phenomena, the lighting and color effects in one
eye differing from those in the other in actual viewing.

Considerable advance has been made in devices for taking and
showing stereoscopic pictures on a single film, and present experi-
ments are very promising.

There are, very naturally, some problems to be cleared up. Photog-
raphers need to learn (1) limitations, or what they should not ex-
pect to do with stereoscopy and (2) still more important, what its use
means in opening up new possibilities — in other words, the technic of
using this new tool. There is some evidence to show that a new sense
of space must be acquired and a much more painstaking and thorough
use of the fact that space is now an ally, not something to be avoided
or faked. The color possibilities deserve very careful study, and

608 G. W. WHEELWRIGHT [J. S. M. P. E.

undoubtedly a new lighting technic will be needed to supplement
what is already known and being used. In particular, this is a very
powerful tool for greater reality in close-ups. What were flat surfaces
now become solid, plastic objects. Stereoscopy provides the ideal
medium for rendition of shades, the finest wrinkle, the texture of the
skin — all the niceties that, summed up, create the impression that
one would actually have if he were really experiencing a close-quarters
reaction to the actress or actor. In all probability, many long and
middle-distance shots that were previously required to give the sense
of space will now become unnecessary. Conversely, many long shots
that had to be avoided because of the difficulty of showing the actual
space involved will now be a possibility to the picture technician.
All in all, it presents a very interesting and exciting medium for
imaginative workers to utilize.

These are the problems and interests of picture taking. Theaters
will need to know any changes in the method of projection that may
be necessary. Fortunately, these appear to be slight; and, in general,
where single-picture projection was really satisfactory, stereoscopic
projection will with small modification be similarly satisfactory.
As in the case of single-picture projection, there is a best viewing
position. The area around this position in which viewing is still ex-
cellent is at least as large for stereoscopic as for ordinary pictures.
The final problem lies in the distribution of glasses and their possible
reuse.

Lumiere in France has apparently successfully solved this problem
through the sale of expensive glasses to those who wish to use them
and own them permanently, and the loan of cheaper glasses that are
taken back after each performance and sterilized. At the New
York Museum of Science and Industry where four presentations of
stereoscopic movies are held daily, it has been found thoroughly
practicable to take back the glasses and use them over and over again,
with a disinfecting treatment after each such use. (After all, the uten-
sils we use daily in restaurants and other public places constitute a
similar problem in antisepsis).

When 35-mm. color motion pictures are taken with the proper
technic and projected full-size upon a large screen, the result to the
observer will be living movies. The audience will be sitting at a
window and seeing the actual scenes and the living actors as if present
in the scene. The screen disappears; one is no longer conscious of
looking at a flat surface. Objects stretch back from the frame of the

Dec., 1937] STEREOSCOPIC MOTION PICTURES 609

screen to Infinity and can even be made, if desired, through a known
technic in taking the picture, to come right out of the screen toward
the audience.

Through light we receive probably 85 per cent of our external im-
pressions of the world, and there are three fundamental principles in
its use. The first two, color and intensity, have long been with us.
The third, polarization, is being made practical for the first time
through Polaroid, the invention of E. H. Land of Boston.

Ordinary light can be said to vibrate in all directions at right angles
to the direction in which it is travelling. Polaroid is made up of a
multitude of submicroscopic crystals, each having polarizing proper-
ties, all lined up perfectly and immovably embedded in a transparent
sheet. The effect of these crystals is to absorb vibrations along one of
their axes. Such alterations of light are not obvious to the viewer
unless he have a second piece of Polaroid with which to observe it.
However, if a second sheet of Polaroid is placed in front of the lighted
area, all goes dark when the axes are crossed, or light when the axes are
parallel. (Incidentally, when a cellophane design is placed between
the two pieces of Polaroid, this colorless, transparent material lights
up with colors that can be reproduced at will and that are permanent;
and as the front Polaroid screen is rotated, the colors gradually
change to their complementary opposites. For the first time it is
possible to have large designs or plain colored areas that are change-
able at will, permanent, and reproducible.) Now, if the front Polar-
oid screen be removed and the observer put on his Polaroid glasses, his
left eye sees the screen clearly; the right eye view is dark. If he tilts
his head far over to the side, or removes the glasses and holds them
vertically, he will see that now the right eye is transparent and the
left eye dark. When taking the picture no such material was used.
This same device used in front of the projector, or one similar to it, is
mounted upon the camera to take two pictures eye-distance apart
and place them upon the film side by side. These two pictures are
projected again through this device, and upon leaving the device the
two eyes are again separated. At this point each eye has a piece of
Polaroid placed in front of it. The right one transmits horizontal vi-
brations and the left one vertical, exactly as the glasses are arranged.
The right eye sees the right-eye picture but not the other. Con-
versely, the left eye sees the left-eye picture and not that intended for
the right eye. The essential condition that each eye see its own pic-
ture and only its own picture is achieved. There is nothing to be ad-

610 G. W. WHEELWRIGHT [J. S. M. P. E.

justed mechanically or otherwise. One forgets the glasses and looks
at the living scene unfolding itself before him; and best of all, the
eyes behave as they would if they were present at the scene. They
converge when the objects are near and change their convergence for
varying distances as they normally would do in life.

(A very interesting demonstration of stereoscopic motion pictures in color (Koda-
chrome) was given immediately after the presentation of the paper.)

REFERENCES

1 TUTTLE, H. B., and MCFARLANE, J. W.: "Introduction to the Photographic
Possibilities of Polarized Light," /. Soc. Mot. Pict. Eng., XXV (July, 1935), No. 1,
p. 69.

2 KENNEDY, C. : "The Development and Use of Stereo Photography for Educa-
tional Purposes," /. Soc. Mot. Pict. Eng., XXVI (Jan. 1936), No. 1, p. 3.

DISCUSSION

MR. BRADLEY: What is going to be done about eye-strain in using these
glasses?

MR WHEELWRIGHT: The question is well taken. The pictures we showed were
taken by an amateur and were not perfectly projected. There is no reason why
there should be any eye-strain, but there are a number of reasons why in photo-
graphing or in projecting, differences in image size can be mistakenly or in-
tentionally produced. Also, individual glasses may show imperfections.

MR. BRADLEY: If the glasses were made according to prescription by a skilled
optometrist, could that be overcome?

MR. WHEELWRIGHT: Yes, entirely. Polaroid is being worn in front of the
eyes now for hours and hours on end, with no noticeable eye-strain when properly
mounted. There is nothing inherent in polarization that would lead to eye-
strain that we can discover.

MR. RICHARDSON: What is the effect, if any, of distance from the viewing
screen?

MR. WHEELWRIGHT: We have to be careful about foreground objects and
background objects. Exaggeration of interocular distance is very valuable in
triangulation ; for instance, when photographing from an aeroplane, in order to
make very small differences of elevation stand out. But in such cases we would not
show the pictures as these are shown, because there would most certainly be eye-
strain. We must also consider the permissible viewing area. With a 16-mm.
projector and 16-mm. film area, we are straining matters in showing the pictures to
200 persons. With 35-mm. film the permissible viewing area is larger. Actually,
there is only one very small area where everything is exactly accurate, but there
is a large area in which things are what might be termed permissibly accurate.
Frankly, that area has yet to be determined.

MR. EDWARDS: Is it not possible that apparent eye-strain is caused by having
one glass adjusted horizontally and the other vertically?

Dec., 1937] STEREOSCOPIC MOTION PICTURES 611

MR. WHEELWRIGHT: There is no reason why polarization in different planes
should cause eye-strain. If one were viewing reflected glare, where polarization is
a function of the angle at which the glass is set, there would be a very definite
reason for eye-strain. Here the two pictures are of the same brilliancy, and the
glasses are supposed to be crossed properly. Professor Kennedy has had glasses
made according to his prescription, and has worked for periods of eight and ten
hours doing nothing but viewing pictures without eye-strain. However, by
looking at the same pictures under improper conditions, it is very easy to ex-
perience eye-strain; and, unfortunately that is a thing that is sensed after the
damage has been done, and not before.

MR. FINN : The proportion of those who experienced strain seems to be about
the same in the fore part of the room as in the rear. I seemed to detect certain
lapses of registration, and it occurred to me that such defects of registration and
eye-strain go hand in hand.

MR. WHEELWRIGHT: Some eyes are better stereoscopically and stronger than
others. I am trained to use my eyes to such an extent that I am a very poor
guinea pig to try the pictures on. I find it difficult to tell when the pictures are
properly or improperly shown when slight strains are being caused. People with
sensitive eyes, or who use one eye to the exclusion of the other, are very much
more conscious of eye-strain than I. I can assure you that pictures can be properly
taken and can be properly shown so there is no eye-strain.

MR. FREEDMAN : When I permitted my head to tilt to one side, the registra-
tion became inaccurate.

MR. WHEELWRIGHT: That is correct. The reason was that the planes of
polarization are fixed as regards the projector, but you change the planes of
polarization of the glasses when you tilt your head. The effect can be overcome
by another method of polarization into which I do not now care to go.

MR. GRIFFIN: Mr. Wheelwright in his paper sketched briefly the history of
stereoscopic systems, and I think it might be well to include in this history
mention of the system known as "Teleview" which did not require that the
audience wear glasses. The system was installed in the Selwyn Theater, New
York, sixteen or seventeen years ago. It consisted in projecting two-eye pictures
from two projectors running synchronously, the unit driving the projector motors
being connected through a distributor driving small synchronous shutters con-
nected to the seats for each viewer. The shutter cuts off alternately the left- and
right-eye pictures so that the results were identical with those we are getting
here.

MR. RICHARDSON: What effect would the usual faults of the eye have upon
viewing these pictures? What would be the difference to men with or without
spectacles?

MR. WHEELWRIGHT: As far as we have determined to date, if an observer
wears his proper glasses, or if he has glasses made of this material and properly
corrected for his eyes, he should have no trouble that he does not already have in
normal viewing.

MR. KELLOGG: How good is the screen in preserving the polarization? Can
you scatter the light as much as needed without loss of polarization? What is
the tolerance, or how much must the image for the wrong eye be reduced for
practical purposes? How does the effect depend upon the general illumination

612 G. W. WHEELWRIGHT [J. S. M. P. E.

level? It seemed to me as if some of the figures were distinctly out in front of the
screen. How does that effect change with distance from the screen?

MR. WHEELWRIGHT: If the screen has a metallic surface, or certain other
surfaces that are satisfactory, there will be no loss of polarization. Certain other
surfaces are completely unsatisfactory. For example, a plain white surface is
very bad; an aluminum screen is practically perfect. There are all sorts of
variations between. The screen we are using has been abused to such an extent
that I was going to send it back and have it properly done, but I did not have time.

MR. KELLOGG: To what extent must you suppress the unwanted image?

MR. WHEELWRIGHT: Fairly completely, depending upon the lights and darks
in adjacent areas. In other words, if a picture is of the same order of brightness
throughout, then polarization will have to be very complete. In these pictures
it is fairly complete, provided you hold your head substantially parallel to the
projector, which most persons do by choice to get the best registration. That
is the secondary problem, since we know a way of getting around it completely
if it seems to be a serious problem.

MR. KELLOGG: Presumably the higher the level of illumination, the more
exacting the requirements for suppression.

MR. WHEELWRIGHT: That is right, and the greater the differences. The
out-in-front effect is controllable at will. In some of these pictures it is being
shown to a greater degree than I should have chosen. We know the laws now
well enough to control it, and in making a commercial or semi-commercial film
we can completely control whether it occurs in front or in the background, or to
what degree.

MR. KELLOGG: Does the out-in-front effect depend upon the distance of the
observer from the screen?

MR. WHEELWRIGHT: To a minor degree. If you sit very far back from the
screen the depths are exaggerated. If you are very, very close, there is a sense
of intimacy, but not so much depth as would be seen from way back. From the
side, as long as each eye sees substantially the same brilliancy as the other, you
will get a better sense of reality in the pictures than in a normal flat picture,
wherein everything becomes distorted when viewed from a point at the side. We
can control that with the metallizing of the screen, something we have been
studying on the side. There has to be some metal in the base of the screen.

MR. MOLE: Have enough persons viewed these pictures to provide statistical
information on possible anomalies in vision. I noticed, for example, what may
be an individual idiosyncrasy, though nobody commented upon it— a secondary
image off to the side of the screen.

MR. WHEELWRIGHT: That is what might be called a vignetting problem.
Since these pictures were taken and this projector built, the effect has been com-
pletely eliminated in the laboratory.

MR. SCHULTZ: I noticed when looking through these glasses that a great deal
of light seemed to be lost. Have you information on the proportion lost, or is
it that the glasses are imperfect?

MR. WHEELWRIGHT: That is not because the glasses are imperfect; that is the
penalty we pay for polarization.

MR. SCHULTZ: Would the average theater be required to increase its screen
illumination?

Dec., 1937] STEREOSCOPIC MOTION PICTURES 613

MR. WHEELWRIGHT: Something would have to be done about the problem.

MR. FRIEDL: You stated that the surface of the screen must be metallic.
Ordinarily, I regard reflections of non-polarized light from metallic surfaces to
be partially polarized. If in projection you use polarized light, will not the
reflection from the screen depolarize it?

MR. WHEELWRIGHT: Polarized light can be scattered to a great degree and
remain polarized, or it can be reflected from a surface and still retain some degree
of polarization. There is a difference in reflection from metallic and non-metallic
surfaces. To retain polarization to a great degree the surface must be metallic
or partly so. Fabric surfaces destroy the effect, depending upon the pigment and
texture of surface. It is quite complicated.

MR. LEWIS: Am I correct in understanding that the stereoscopic pictures can
be shown in the usual projector?

MR. WHEELWRIGHT: Yes, with a supplementary lens or device in front of
the lens.

MR. LEWIS: Is is not necessary to reduce the width of the picture, as shown
here?

MR. WHEELWRIGHT: As I mentioned in the paper, this equipment is experi-
mental. There is no reason why the frame shape should not be the same. There
will, however, be less film area per eye view than there would be with ordinary
pictures, but if you take the two eye pictures and add them up, there will be the
same amount of information for the two eyes as before, but subdivided in a new
way.

MR. LEWIS: If you used the standard 35-mm. projector and projected the
pictures in the same size of room, would you have to reduce the area of the pic-
ture?

MR. WHEELWRIGHT: In very large-sized projection you certainly would have
to reduce the picture or increase the light. In the smaller pictures we think we
can get away with it.

REPORT OF THE PROJECTION PRACTICE COMMITTEE*

Summary. — Among the important projects under consideration by the Committee
are (1) a survey of theater characteristics, as regards screen sizes and brightnesses;
viewing angles and areas; projection angles and auditorium dimensions; and equip-
ment in use; (2) a study of screen illumination; and (3) investigation of fire hazards.

The major portion of the report deals with a proposed revision of projector aper-
ture dimensions by the Academy of Motion Picture Arts & Sciences, and the Com-
mittee's arguments for disapproving the proposals.

The Committee does not propose at this time to present a formal
report. The present informal report results from the fact that the
Committee's many records and data in constructive directions are as
yet only partly analyzed, and are so bulky that a compressed final
report is not possible at this meeting. However, aside from the sub-
jects upon which the Committee has been engaged for some time,
the latter portion of this report will be devoted to a discussion of the
recent proposal of the Academy of Motion Picture Arts and Sciences
to modify the existing projector aperture. The importance of com-
menting at length upon the proposal is particularly great in view of
the wide publicity that has recently been given to it and the fact that
the Projection Practice Committee is unanimous in its opinion that
the proposal has not taken into account all the exigencies of projec-
tion and is ill-advised in the present state of the art. The American
Projection Society concurs in the finding of the Projection Practice
Committee.

Some of the more important subjects upon which the Committee
has been most active during the past six months are as follows :

(a) Survey of Theater Dimensions. — In this survey numerous im-
portant theater constants have been widely investigated, and the
corresponding reports are now under survey. Forms were circulated
among the theaters of the country asking for information concerning
such features as screen sizes, viewing distances, dimensions of the
theaters, and other items of importance in projecting and viewing
motion pictures. The data thus far collected are very extensive
and complete, and when analyzed will give a clear picture of the situa-

* Presented at the Fall, 1937, Meeting at New York, N. Y.; received October
9, 1937.
614

PROJECTION PRACTICE COMMITTEE REPORT 615

tion at present confronting projection in theaters of all classes. As
a corollary, the knowledge thus gained of existing projection condi-
tions will lead to a number of constructive recommendations and pro-
posals for the improvement of these conditions.

(b) Study of Screen Illumination. — This survey has required a
study of screen illumination and brightness meters, as well as methods
of measurement and their practical applications.*

(c} Investigation of Fire Hazards. — Methods of minimizing the like-
lihood of fire in projection rooms and proposals leading toward uni-
form fire-prevention regulations have been among the subjects
handled by the Committee. The great volume of assembled data now
under study will require further time for its coordination and analy-
sis and will be presented to the Society in due course.

ACADEMY PROJECTOR APERTURE PROPOSAL

In view of the fact that essential action photographed upon the
film is often cut off from the screen during the process of projection,
the Projection Practice Committee of the Society offered at the Holly-
wood Convention last May,1 the recommendation that cameramen
draw upon the ground-glasses of their view-finding devices, hair-line
rectangles that could be used as guides or danger signals in composing
their scenes. Specifically, the proposal was to inscribe upon the
ground-glass a hair-line rectangle 0.815 X 0.590 inch, which would
be slightly within the dimensions of the standard projector aperture,
which are 0.825 X 0.600 inch. To avoid misunderstanding, it should
be emphasized that this would make no change in the photographic
area of the film, but would act only as a warning to the cameramen
that the heads or feet of their actors are approaching the points at
which their images will not be projected upon the screen in the thea-
ter. By adopting dimensions slightly smaller than the existing
projector aperture dimensions, allowance was made for screen mask-
ing, film weave in the projector, keystone effect, etc.

On September 16, 1937, the Academy of Motion Picture Arts and
Sciences issued a memorandum dealing with proposed revisions of
the dimensions of the standard projector aperture, the stated purpose
being to decrease the possibilities of cutting off the images of the heads
and feet of actors from the screen. Among other alleged advantages

* The Committee notes with approval a campaign for improved screen illumi-
nation resulting from improvements in the projector arc, sponsored widely in the
press by a prominent industrial organization in the field.

616 PROJECTION PRACTICE COMMITTEE REPORT [j. s. M. p. E.

were superior pictorial composition of the scene during production
and the facilitating of composite and process shots, etc. Specifically,
the proposal was that the dimensions of the projector aperture be in-
creased to 0.615 X 0.846 inch, and that the projector aperture be
moved laterally so that its center-line will coincide with the center-
line of the camera aperture.

The Projection Practice Committee is unable to concur in the Acad-
emy's proposal for several reasons:

(a) Film Shrinkage and Weave. — At the time the present dimen-
sions of the projector aperture (0.825 X 0.600 inch) were established,
careful consideration was given to the extent of shrinkage and weav-
ing of the film, and it was felt that the dimensions arrived at rep-
resented a limit that did not leave much margin of safety with respect
to framing the picture in the aperture. The combined effect of
shrinkage and weaving during film travel, occurring throughout the
photographic, processing, and projection processes, even at present
may lead to a danger of non-framing of the picture by the projector
aperture. Before any attempt is made to encroach upon the small
margin of safety now remaining, careful consideration should first
be given to the maximum lateral film shrinkage and weave, and pres-
ent and past releases should be checked to determine how closely
the studios and laboratories are maintaining present-day standards.
Everyday experience shows that there is great variation in the lateral
displacements of the picture on the film as well as of the sound-track.
Under these circumstances the adoption of the Academy proposal
would often permit the lateral frame line of the camera aperture to
appear upon the right-hand side of the screen, and in extreme cases
even the images of the sprocket-holes might appear in the picture.

In the present standard a difference of 0.0065 inch is allowed be-
tween the center-lines of the camera and projector apertures, this
allowance being made to compensate in some measure for film shrink-
age, and to prevent the appearance of the camera aperture edge upon
the screen. The difference was allowed in one direction in view of
the fact that the shrinkage occurring subsequently to photographing
is regarded as always in the same direction: namely, toward the
guided edge of the film (which is the fixed datum). Such allowance
is not included in the Academy proposal, in view of the fact that the
camera aperture and projector aperture center-lines are made to co-
incide.

It may be contended that shrinkage by itself may not be sufficient

Dec., 1937] PROJECTION PRACTICE COMMITTEE REPORT 617

cause for concern ; but combined with weaving and other inaccura-
cies occurring during the many processes through which the film must
pass, the combination of all these effects is likely to result unfor-
tunately. Cognizance should also be taken of the considerable
variation that occurs not only in general release prints, but particu-
larly with respect to title apertures in domestic releases, and foreign
apertures in general, particularly in news shots.

(6) Photographic Composition. — The claim was made that by in-
creasing the projector aperture 21 mils in the horizontal dimension,
and 15 mils in the vertical dimension, opportunity would be afforded
the cameraman to compose his scenes more artistically and dramati-
cally. Simple calculation shows that increasing the dimensions of the
present standard projector aperture to the proposed values will result
in an increase of area of projected aperture of only five per cent. In
linear dimensions, this would mean an addition to a 20 X 15-foot
screen picture of only three inches on each side and 2x/4 inches at top
and bottom. It is exceedingly doubtful whether such small in-
crease in linear dimensions would add appreciably to the dramatic
delineation, particularly when the industry at various times has
seriously considered widths of film up to 50 and even 70 mm. as nec-
essary for adequate improvement of dramatic scope. In view of
the 50 or 100 per cent enlargement of scope required, therefore, the
2l/2 per cent proposed increase is obviously negligible. It is just as
obvious that appropriation of even the few thousandths of an inch
still remaining for safety during projection would never in any rea-
sonable sense achieve the photographic improvement sought for, up
to the limit of the 35-mm. film. Furthermore, the fact must be
taken into account that the effect of the picture upon the spectator
is a function not only of the size of the picture upon the screen, but
also the distance of the viewer from the screen. Considering the
average viewing distance found in theaters, it is felt that the effect
of a 2J/2-per cent increase in the dimensions of the screen picture
will be negligible. The angle subtended by a 20-foot, six-inch
screen at the eye of a spectator seated 50 feet from the screen would
be exactly the same as if the spectator were viewing a 20 -foot
screen I1/ 4 feet nearer.

Although the remarks made above have been specifically con-
nected with screen images, it is obvious that they apply equally well
to studio sets and camera images. The Projection Practice Commit-
tee is sympathetic toward any attempt to improve photographic com-

618 PROJECTION PRACTICE COMMITTEE REPORT [J. s. M. P. E.

position, scope of scenes, size of aperture plates, etc., that would re-
sult in any real advantage; but it is the Committee's feeling that
the change, to be justifiable, would have to be entirely more substan-
tial than is possible in existing mechanisms. In the case of the
Academy's proposed s- jecifications, it is the Committee's feeling that
any advantage resulting therefrom will be negligible, and the diffi-
culties attending the introduction thereof into existing practice would
be very serious, as out-ined in other sections of this report.

(c} Screens and Masking. — It is obvious that any enlargement of
the projector aperture will produce an enlargement of the screen
image, and that consequently the screen will have to be remasked.
Moving the masking is in itself a fairly expensive job; but, in addi-
tion, it should be borne in mind that the screens in thousands of thea-
ters throughout the country are by no means new. Many of them
are quite dirty and discolored, and moving the masking will leave a
white border around the edges of the dirty and faded portion. A two
or three-inch white strip around the edge of a 20-foot screen
would be bad enough in the case of black-and-white projection, but
it is obvious that the situation would be still more unfortunate when
color-pictures are projected. This means, then, that either the
screen must be cleaned or otherwise renovated, or a new screen must
be purchased.

(d) Cost. — It is extremely difficult to estimate exactly what the
cost would be to effect a change from the present standard to the pro-
posed dimensions. However, a fair idea may be gained by remem-
bering that there are approximately 16,000 theaters in the United
States that would be forced to buy new apertures, shift the screen
masking, and probably be required either to renovate their screens
or buy new screens. It is estimated that the change could not be
effected even in small theaters for less than $50, and may amount
to as much as several hundreds of dollars when necessary to pur-
chase new screens. It is probably not too much to anticipate that
the cost to the exhibitors of the country would be in the neighborhood
of $1,000,000. In addition, it is obvious that all theaters could not
make the change at the same time. Many theaters are in financial
difficulties, and many others may not find it convenient to make the
necessary expenditure. Accordingly, introduction of the proposed
aperture would extend over a considerable period of time during
which much confusion and many poorly projected pictures would re-
sult.

Dec., 1937] PROJECTION PRACTICE COMMITTEE REPORT 619

Theaters that could not afford to make a complete change im-
mediately, could, of course, install the proposed aperture; but in that
case the picture would spill over upon the masking. If they persisted
in using the present standard aperture, while the cinematographers
were taking advantage of the enlarged photog aphic area by allowing
their actors to approach closer to the limits' of the ground-glass in
their view-finder, such theaters would be cutting off more of the
heads and feet than ever before.

Conclusion. — The Projection Practice Committee is unanimously
opposed to the Academy's proposal for the reasons given above. The
American Projection Society also concurs in 'this action of the Pro-
jection Practice Committee. Furthermore, the proposed aperture
would not accomplish the objective of the original SMPE proposal
last spring, namely, to provide the cinematographers with a hair-line
as a danger signal, within the. area enclosed by which they should
keep their action. Even were a larger aperture accepted, such a
danger signal would still be necessary.

The Society's proposal remains the simplest, speediest, and least
expensive method of avoiding edge-of-frame cut-off on the screen.
On the other hand, the Academy's proposal is a major, extended, and
costly matter.

Accordingly, the Projection Practice Committee hereby reaffirms
its original proposal and strongly urges its general adoption.

H. RUBIN, Chairman

]. O. BAKER A. N. GOLDSMITH E. R. MORIN

T. C. BARROWS A. GOODMAN M. D. O'BRIEN

F. E. CAHILL H. GRIFFIN G. F. RACKETT

J. R. CAMERON S. HARRIS F. H. RICHARDSON

A. A. COOK J. J. HOPKINS B. SCHLANGER

J. K. ELDERKIN C. F. HORSTMAN C. TUTTLE

J. J. FINN D. E. HYNDMAN J. S. WARD

R. R. FRENCH J. J. KOHLER V. A. WELMAN

E. R. GEIB P. A. McGuiRE A. T. WILLIAMS

REFERENCE

1 Report of the Projection Practice Committee, /. Soc. Mot. Pict. Eng., XXIX
(July, 1937), No. 1, p. 48.

DISCUSSION

MR. GOLDSMITH: This recommendation of the Committee to the Society was
arrived at not only at one meeting of the Committee, but at a special meeting
which ran for many hours and considered it in great detail; and then again during

620 PROJECTION PRACTICE COMMITTEE REPORT [j. s. M. P. E.

the preparation of the report, which took many more hours of the time of a special
committee that drafted it, after which it was approved. It probably represents
as careful thought, as unanimous opinion, as we have yet been able to give any
similar subject. In our deliberations, practical theater men, active projectionists,
supervisors of projection, and engineers, all reached the same viewpoint without
difficulty. There was not, so far as I know, a dissenting voice at any time.

MR. RICHARDSON: I move that the Projection Practice Committee be com-
plimented upon the excellence of its work and that its recommendation be ap-
proved. (The motion was seconded.)

MR. CRABTREE: I think the intent of the Academy recommendation is good.
They are anxious to make the maximum possible utilization of the space available
on the film, which we will admit is none too large. We have talked for many
years of going to wider film. The Academy is trying to make more effective use of
the film. The main objection appears to be the cost.

MR. GOLDSMITH: I must disagree on that point. It is not a fact that the major
objection raised by the Projection Practice Committee is the cost, burdensome,
inopportune, and unnecessary as that may be, and leading, as it might, to no
result commensurate with the cost. That is not the only objection. The principal
objection is that the dangers to correct projection, due to weave, shrinkage, and
other factors, as pointed out in the report, are such that the Committee is fully
persuaded that not only would the change be costly, but that it would be unsuc-
cessful, resulting in the projection of frame lines and cutting off picture edges by
screen masking beyond what now occurs. In other words, the Committee is
persuaded that there is no present practicable way of expanding pictures within
the dimensional film limits of today. We have already gone to the very limit of
utilization; and, indeed, certain members of the Committee are doubtful whether
(considering the effects of projection angles, film shrinkage, printer and projector
weave, and all the rest of the inevitable things that occur in daily practice) we
have not already gone too far in widening the aperture. They view with justified
alarm any further increase.

The hair-line proposed by the Committee was intended as a convenient and
cooperative measure for the cameraman. He could then compose his scenes beyond
the hair-line if he so desired, but when he saw the essential action approaching
the hair-line, he would know that it was time to be careful.

It is an excellent general principle to make railroad cars as wide as possible;
and thus if there are four inches between opposite passing trains at present, we
might like to widen each train 1.99 inches, and, as a result, have wider cars. The
only trouble with that would be that on a curve, or when the cars were swaying,
passing each other at 80 miles an hour, the effect would be disastrous.

The situation here is parallel. We are in a dangerous situation. The proposal
not only makes a dangerous situation worse, but invites real disaster.

MR. JONES: This seems suspiciously like standardization. Should we not
handle this as we would a standard, following our usual letter-ballot procedure?
Of course, we may obtain an expression of sentiment here this morning, but I do
not think we can take any official action. Should not the matter be referred to
our Standards Committee?

MR. GOLDSMITH : The resolution was simply that the report of the Projection
Practice Committee be approved. The Projection Practice Committee's report

Dec., 1937] PROJECTION PRACTICE COMMITTEE REPORT 621

does not suggest any new standards; it merely opposes the introduction of a
proposed new standard. The Academy has released to the trade press, with wide
publicity, a new proposed standard for consideration, which, in the Committee's
opinion, is damaging and objectionable. All that is proposed here is that this
standard be not approved and the Committee's original suggestion be approved,
and that the Society uphold the Committee's viewpoint.

MR. EDWARDS: I tried the proposed aperture in a first-run house. A Warner's
first-run feature showed a black band at the right-hand edge of the screen, and a
Fox newsreel showed the sound-track on the left-hand side.

MR. SCHLANGER: The small gain of 5 per cent is inconsequential in comparison
with what might be accomplished with a little care by the cinematographer to
utilize the limits he now has. Using greater care in the cinematography will pro-
duce, not a physically larger scene, but an effectively larger scene; in other words,
carefully studied action placement will produce action area on the screen that
will be relatively much larger than the 5 per cent physical gain proposed.

MR. GOLDSMITH: The question has been called for. All those in favor of ap-
proving the Report of the Projection Practice Committee as read will signify by
saying "Aye."

Contrary?

It is an unanimous vote.

STANDARDIZATION OF PHOTOGRAPHIC DENSITOMETRY*
CLIFTON TUTTLE AND A. M. KOERNER**

Summary. — It is desirable that all laboratories dealing with photographic prob-
lems shall be in agreement upon the significance of the term "density," and that the
means for numerically determining this value shall be specifiable.

In different optical systems, the apparent "light-stopping power" of a given photo-
graphic image will vary because of the manner in which that sample reflects, scatters,
and absorbs light. Since the numerical value obtained depends upon the characteristics
of the optical system used in the densitometer, it becomes necessary to specify the optical
system to be used as a reference standard. Because it may be definitely specified, the
integrating sphere is suggested as the light-collector for this standard optical system.
Precautions that must be followed in using the sphere are enumerated.

It is shown that once some standard optical system is adopted, several other types of
optical systems may be employed in practical instruments if the instruments are cali-
brated under actual working conditions with photographic images previously mea-
sured in the system adopted as standard.

The paper concludes with a discussion of the interrelationships of logn, apparent
opacity as determined in several optical systems commonly used in densitometry.

The standardization of densitometry is an issue of increasing impor-
tance to photographic research in general and to the motion picture
industry in particular. It is desirable that the various laboratories
engaged upon photographic problems shall be in agreement as to the
significance of the term "density," and that they shall be unanimous
within the limits of purely observational errors, in their assignment of
a numerical value of density to any particular specimen, regardless
of the type of instrument used in making the necessary measurements.
As a contribution toward such a universal understanding, a rather
complete analysis of the problem has been reported to the Optical
Society of America.1 The present paper is the result of a request
from the SMPE Standards Committee for a brief discussion of our
conclusions.

Three characteristics of a developed photographic image are respon-
sible for variations in the apparent value of density that appear when

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
13, 1937. Communication No. 625 from the Kodak Research Laboratories.

** Eastman Kodak Co., Rochester, N. Y.
622

PHOTOGRAPHIC DENSITOMETRY 623

the image is used in different optical systems : (1) the light-scattering
property, which results from the inhomogeneous nature of the image,
(2) the light-reflecting property, and (5) the light-absorbing property.

In the above-mentioned paper1 we have attempted to show quan-
titative results for the combination of these three factors in several
densitometer optical systems. The reader interested in the numeri-
cal results is referred to the original paper, but, for the present pur-
pose, we wish to point out in a qualitative manner the nature of the
discrepancies arising from each of the three inherent characteristics
of the photographic image.

As an example of variation in apparent density caused by scattering,
consider the use of an image in a projection system as compared with
its use in a contact printing system. Since the projection objective is
appreciably removed from the image, it collects the image-transmitted
light within only a limited angle, while the contact print utilizes
practically all the transmitted light. Thus, it is possible that if the
incident light is collimated in the projection system, half of the trans-
mitted light will be scattered outside the angle of collection, with the
result that the light-stopping power, or density, of the image appears
greater than it does in the contact printing system.

To illustrate the influence of reflection upon the apparent value of
density, consider the case of two conventional densitometers, the first
of which uses as a diffusing material opal glass of high reflectance, and
the other, a diffusing material of which the reflectance is lower. Pho-
tographic images have a surface reflectance of the order of ten per cent.
If the first opal reflects eighty per cent of the incident light, then the
product of eighty and ten, or eight per cent, is added to the incident
light by first-order reflection from the image and re-reflection from the
opal. If the second opal reflects only forty per cent, the increment
that results from interreflection will be only half as much, or four per
cent. Density will, of course, appear higher in the second case. If
the reflection coefficient of the image were constant, the result of the
interreflection effect would be a constant difference in density. How-
ever, the matter is further complicated by the fact that the reflection
coefficient varies with density, decreasing as density increases.

The third property of a photographic image that gives rise to dis-
crepancies in the value of density as measured in different optical sys-
tems is absorption within its finite thickness. Since absorption of light
takes place throughout thin finite layers, the light-stopping power
of the image for a single ray will depend upon the angle at which

624 C. TUTTLE AND A. M. KOERNER [J. S. M. P. E.

that ray passes through the image. Consider the case of a diffusely
illuminated photographic density: If the transmitted measured
light includes only rays normal to the surface, the density will have
its lowest value. If rays of light that pass through the layer at
angles other than the normal are included in the measurement, the
numerical value of density will be increased. As a concrete example,
suppose that an image is placed in contact with an illuminated opal
glass of small diameter and that the transmitted light is measured by
means of the response of a photoelectric cell to light entering its win-
dow. Suppose first that the cell is placed at a considerable distance
from the sample. It will collect then only the transmitted rays
emerging in the nearly normal direction. If the cell window is
brought closer to the sample, it begins to include more and more of
the rays that have traversed longer paths through the absorbing ma-
terial, and the resultant apparent density increases.

From the above, it is apparent that discrepancies in density mea-
surement arise because certain characteristics of the measuring
optical system interact with the characteristics of the material.
Thus, the angle of collection of the optical system is intimately linked
with the light-scattering and the light-absorbing properties of the image.
Also, the light-reflecting properties of the optical system interact with
the light-reflecting properties of the image. From a consideration of
this fact, we immediately arrive at two definite conclusions, which are
of importance in any discussion of the possibility of interlaboratory
standardization of densitometry : (1) A standard instrument can not
be specified without accurately specifying the characteristics of its
optical system that interact with the material characteristics; (2)
densitometers can not be calibrated by means of arbitrary standard
absorbers of light unless the characteristics of the standards are iden-
tical with those of the photographic image.

To illustrate these statements more fully, suppose that the conven-
tional opal densitometer were to be accepted as the primary standard
instrument. As a consequence of our first conclusion, it is obvious
that the reflecting properties and the diffusing properties of the opal
would have to be accurately specified. In addition, certain dimen-
sions of the optical system that determine the angle of collection would
have to be rigidly observed. The matter of dimensions presents no
difficulty, but the characteristics of opal glasses are not easily speci-
fied or easily determined ; nor are materials to meet such rigid speci-
fications easily obtained. However, if a primary standard instru-

Dec., 1937] PHOTOGRAPHIC DBNSITOMETRY 625

ment could be located at a central point, geographically, and read-
ings from it transferred to other densitometers by means of calibrated
standard densities, the plan might be feasible. The question immedi-
ately arises as to the nature of the standard densities. Various stand-
ards have been suggested, only one of which we shall discuss at
length in order to illustrate the application and importance of the
second conclusion just given.

It has been proposed that semi-transparent metallic layers deposited
by cathode sputtering or by evaporation upon glass be used as stand-
ard densities. A series of such standards might be extremely use-
ful, since with proper treatment they could be made permanent and
rugged. Actually, however, they have no value as standard den-
sities, since they fail to represent photographic images satisfactorily.
In the first place, they owe their apparent density almost entirely to
surface reflection and very little to absorption. Hence, when used
in conjunction with opal glasses, the interreflection effect is very large,
and large variations in apparent density result as variations in opal
reflectance occur. Also, since there is very little actual absorption
throughout a finite thickness, the apparent density is practically inde-
pendent of the angle of incidence and collection. Finally, very little
light is scattered in transmission through the metallic films. Thus,
in any densitometer calibrated by means of metallic films, the inter-
reflection effect would be overemphasized, while the diffuseness of
the system or its effectiveness in collecting scattered radiation would
be almost entirely ignored.

Calibration of different types of densitometers by means of other
mechanically contrived light-absorbers, such as calibrated sector
disks, or wire-mesh screens, is likewise open to the objection that the
actual conditions of photographic image measurement are not fulfilled
since such sector disks or screens have very little in common with the
actual photographic image.

Having discussed some of the difficulties we may expect to encoun-
ter, we are now in a better position to proceed with the search for a
standard system of densitometry. In addition to the requirements
outlined above, certain other features are necessary or desirable. We
believe that a prime requisite of such an instrument is that it shall be
easily and precisely reproducible from specifications. A desirable
feature would be that the optical system should be readily usable in a
commercial densitometer and that its results should not differ greatly
from those obtained in the usual opal densitometers.

626 C. TUTTLE AND A. M. KOERNER [J. S. M. P. E.

We have already pointed out our objections to densitometers em-
ploying opal diffusers as standard instruments. A densitometer em-
ploying no diffusion would perhaps be the easiest to specify, but there
are a number of valid objections to the adoption of specular density
as standard density. In the first place, specular density differs greatly
from contact printing density and also from the readings obtained
with any of the numerous opal densitometers in present use. In the
second place, to read specularly the same high-to-low-density range
now being covered by opal densitometers would require that the cali-
bration of the intensity- varying means be extended tenfold or more.
As an illustration, a specular densitometer having a range of 0 to 4.0
might be required to accommodate the same photographic images
that could be read on an opal instrument having a range of 0 to 3.0.

One optical system that we believe to be reproducible to specifi-
cation and that has the additional advantage of giving results that are
numerically close to opal densitometry and to effective contact print-
ing density is the integrating sphere.

The integrating sphere has been employed in many photometric
problems2 since its use was first described by Sumpner3 and Ul-
bricht.4 The device is a hollow ball coated on the inside surface
with a material that is a diffuse reflector of high coefficient. The in-
tegrating sphere owes its usefulness in photometry to the fact that if
it is illuminated by a light-source, any spot on its wall will, as a result
of multiple reflection from other parts of the wall, assume a brightness
proportional to the total flux and independent of the direction of the
flux. The source may be a lamp within the sphere or the light may
be admitted in a narrow beam through a window in the sphere wall.
In either case, according to sphere theory, direct light from the source
should be shielded from the spot whose brightness is to be measured.

Though the integrating sphere has not been frequently used as a
transmission-measuring instrument, there appears to be no reason
why it could not be adopted as a standard device for photographic
densitometry. It avoids most of the weaknesses of other possible
standard optical systems. All the light scattered by the image can
be collected regardless of the direction of scatter. Interreflectance
between the image and the sphere wall plays a very small part in the
measurement. Errors caused by differential absorption of light-rays
transmitted at different angles may be minimized by specifying the
degree of collimation of the incident light.

We feel that a definite proposal of the sphere as the standard densi-

Dec., 1937]

PHOTOGRAPHIC DENSITOMETRY

627

tometer should be accompanied by complete specifications as to di-
mensions and materials, with a definite statement concerning the
tolerances allowable in the dimensions and materials. This can be
done only after the completion of experiments now in progress.
Fig. 1 shows a bundle of rays from a collimating lens entering the
sphere window and being focused upon a spot diametrically opposite
the window. Through a second window ninety degrees from the first,

SOURCE

COMPARISON
SOURCE

OBSERVATION
WINDOW

UUM NE R- BROOHUN
CUBE

TRANSLUCENT I I

PLATE EYEPIECE.

FIG. 1. Arrangement of optical parts, including integrating sphere.

the brightness of the opposite sphere wall is measured by any suit-
able photometer. The photographic material is placed over the sphere
window, the edge of which is shaped so that a straight line on the
emulsion surface becomes a chord of the inner sphere surface.

An opaque screen intercepts direct light from the sphere window to
the spot on the wall whose brightness is to be measured. The loga-
rithm of the ratio of the brightness of this spot with and without the
photographic material in place may be adopted as standard density.

The factors that require specification in this system are :

(1) The allowable departure from collimation of the incident light.

(2) The size of the sphere.

(5) The relative size of the sphere and its openings.

(4) The size of the spot whose brightness is to be measured.

(5) The size of the screen — a consequence of 5 and 4.

(6) The material with which the wall is to be coated.

628 C. TUTTLE AND A. M. KOERNER

Both the theory and the experimental work thus far completed indi-
cate that all these factors may be specified and that all specifications
will have ample tolerances.

Further work will also attempt to define specifically the conditions
to be met by other systems of measuring the wall brightness, espe-
cially those involving photoelectric determinations.

Should the sphere be accepted as the primary standard optical sys-
tem for densitometry, it is quite improbable that it will come into
general use in density-measuring instruments. Opal densitometers,
of which there are so many in general use, will no doubt continue in
vogue, and photoelectric systems of various types will no doubt in-
crease in numbers. In general, laboratory densitometers will not de-
pend directly upon the determination of the ratio of incident to trans-
mitted light, but rather upon the calibration of some intensity-vary-
ing device used in making a photometric match between the trans-
mitted light and a comparison light.

Data published by the authors1 show the feasibility of arbitrary
calibration of the intensity-changing device used in opal densitome-
ters and in several other types of optical systems particularly suitable
for photoelectric densitometers in termsof sphere density. The signifi-
cant fact brought out by those comparative data is that, if the values
of a series of densities on a fine-grained material, such, for instance,
as positive film, are determined with the standard optical system,
and if these values are used arbitrarily to calibrate an intensity-
changing device used for photometric matching in conjunction with
any of several types of optical systems, all other materials may be
read with this calibration and in no case will the error exceed 0.02.
The differences in the essential characteristics of the various materials
are apparently not great enough to invalidate the use of any one of
them as secondary standards for the calibration of these several opti-
cal systems. No other kinds of materials known to the authors can
serve for the calibration of densitometers.

REFERENCES

1 KOERNER, A. M., AND TUTTLE, C.: "Experimental Determination of Photo-
graphic Density," J. Opt. Soc. Amer., 27 (July, 1937), No. 7, p. 241.

2 WALSH, J. W. T. : "Photometry," Constable & Co. Ltd. (London, 1926). A com-
plete bibliography of the integrating sphere, its theory, and uses.

3 SUMPNER, W. E.: "On the Diffusion of Light," Phil. Mag., 35, 81 (1893).

4 ULBRICHT, R.: "Photometer for Mean Spherical Candlepower," Elektrotech-
nische Zeitschrift, 21 (1900), p. 595.

NOTES ON THE VELOCITY MICROPHONE*

M. RETTINGER**

Summary. — // is well known thai the per cent syllable articulation decreases with
increasing distance between the speaker and the microphone or listener. It is shown
that when a velocity-ribbon microphone is set so far behind a pressure-operated micro-
phone that the recorded reverberation is the same for both microphones, the per cent
syllable articulation remains unchanged. Attention is drawn to the undesirable
effects of interference for steady tones, and mention is made of ways to reduce such
interference.

Assuming a room to have no unusual shape and to be untroubled
by a high noise-level, the reverberation in that room becomes un-
doubtedly the most important factor controlling its acoustics. Ex-
cessive reverberation causes a piling up or overlapping of successive
syllables, resulting in considerable loss of intelligibility. When
sound is recorded in such a "live" room, the reproduced sound-pattern
is indistinct or blurred, due to the fact that a microphone represents
but one ear which registers all sounds, wanted and unwanted. This
difficulty can be overcome, if conditions permit, by maintaining a
short distance between the source of sound and the microphone, as
then it is mostly direct sound that is recorded.

But even though a room may not be reverberant for the middle and
the high registers, it may be so for the lower frequencies. Practically
all acoustic materials are less absorbent for the low notes, increasing
rapidly in absorptivity as the frequency becomes higher. Such a con-
dition would then again call for a reduced distance between the
speaker and the microphone, with some resultant loss of "presence,"
as it is mainly the ratio of reflected to direct sound that lends to the
recorded sound-pattern an impression of "liveness" or acoustic
perspective.

It is well known that the velocity-ribbon microphone, due to its
directional characteristics, permits recording sound at a distance 1.7
times that between a pressure-operated microphone and the source

* Received May 10, 1937.
** RCA Manufacturing Co., Los Angeles, Calif.

629

630

M. RETTINGER

[J. S. M. P. E.

for the same amount of "recorded reverberation" or ratio of totally
reflected to direct sound at the microphone. Since the frequency re-
sponse of the velocity microphone is practically constant within its
solid angle of reception — quite unlike that of the pressure-operated
microphone — what sound strikes the microphone is recorded by it
with almost no frequency discrimination, insuring making a faithful
facsimile of sound-pattern, a condition particularly to be desired in
recording music.

Now, it is well known that the syllable articulation decreases with
increasing distance between the speaker and the microphone or

^S

;x>

\

\ ~>

\

J

1.2
2.2

Sec.
3»c

5«c

\

\

\

\

\
\

\

\

C

'

V

V

V

i

\

\\

f-

J

\ \

TICULA
*

\

\ \
\ \

\

\ \

K

, \ \

<

\ v \

£
H *.

\ \

\

1

DISTANCE FROM MICROPHONE IN FEET.
FIG. 1. Effect of reverberation upon syllable articulation.

listener. The question, therefore, arises whether a loss occurs in
articulation when the velocity microphone is moved back of a pres-
sure-operated microphone a distance that gives the same amount of
recorded reverberation. Phrased differently, we may ask whether
the per cent syllable articulation is a function only of the amount of
recorded reverberation, regardless of what the distance is between
the speaker and the microphone.

Fig. 1, due to J. C. Steinberg,1 shows the effect of reverberation
upon syllable articulation in a room 20 X 30 X 15 feet for varying
distances between the speaker and the microphone. It is seen that
there is considerable decrease in articulation with increase in distance,
regardless of whether the room is "live" or "dead."

Dec., 1937]

NOTES ON VELOCITY MICROPHONE

631

The writer has redrawn the curves as Fig. 2, showing equal articu-
lation contours for different amounts of reverberation and change of
distance between the speaker and the microphone.

For a pressure-operated microphone the recorded reverberation or
ratio of reflected to direct sound at the microphone is given by

Er = 167r£>2 (1 - Q)

Ed ' aS

where D represents the distance between the microphone and the

\

\

\

\

\

\

\

\

\

\

\

FIG. 2. Data of Fig. 1 redrawn as equal articulation contours.

source of sound; a, the average absorption coefficient of the ma-
terials in the room ; and S, the total interior surface.

For a directional sound-collecting system, such as a velocity rib-
bon microphone or a unidirectional microphone, the recorded
reverberation is given by

- a) K

E'd

aS

where K represents the solid angle of reception.2

Knowing the shape, volume, and reverberation time of the room
upon which the curves of Fig. 1 are based, we can calculate the

632

M. RETTINGER

[J. S. M. P. E.

recorded reverberation for various distances. When plotting syllable
articulation against recorded reverberation we obtain Fig. 3. It is
seen that syllable articulation is a function mainly of the recorded
reverberation, the curves being separated by no more than experimen-
tal error. Hence we may say that when a velocity microphone is set
so far behind a pressure-operated microphone that the recorded reverbera-
tion is the same for both, the per cent syllable articulation remains un-
changed.

The foregoing is concerned primarily with transient sound-patterns

\

\

*-.

RECORDED REVERBERATION -

DIRECT SOUND ENEIRGY

FIG. 3. Syllable articulation vs. recorded reverberation.

such as syllables. When a sustained tone exists in a room, however,
we are faced with the problem of interference. H. Frey3 has calculated
the probability of existence of a point in a rectangular room where
complete interference exists. By complete interference is meant
that all the reflected sound is equal and opposite in phase to the
direct sound. Frey's curves are shown in Fig. 4. It is seen that the
mean absorption coefficient of a particular room must be at least 0.7
for the improbability of meeting a point of complete interference at a
distance of approximately 20 feet from the source of sound. If we
wish to operate with the certainty of not meeting such a node, we
must either reduce the distance to 6 feet or increase the mean ab-
sorption coefficient to 0.85.

Dec., 1937]

NOTES ON VELOCITY MICROPHONE

633

A partial solution of this problem consists in providing corrugations
upon the walls and ceiling of the room, as thereby to increase the
number of reflections per second occurring at any point in the room.
This can easily be seen by considering the following equation

4v

where N represents the number of reflections per second taking place
at any point in the room; v, the volume of the room; S, the surface of
the room, and c, the velocity of the sound. By providing corruga-

DiSTANCt BETWEEN SPEAKER & MICROPHONE IN FetT

FIG. 4. Probability of complete interference for sustained notes.

tions upon the walls and ceiling we increase the numerator as well as
decrease the denominator, since 5 is increasing and v decreasing.

The undesirable effects of interference during recording can, how-
ever, be lessened still further by employing a velocity microphone.
Experiments4 have shown that velocity nodes and antinodes, when
recorded with a velocity microphone, actuate the microphone less
violently than pressure nodes and antinodes actuate a pressure micro-
phone. This is due to the fact that the kinetic sound energy is made
up of vector velocity components, while the potential sound energy
consists of scalar pressure components. Fig. 5 shows this relation
graphically.

634

M. RETTINGER

FIG. 5. Relation between pressure and particle velocity.

REFERENCES

STEINBERG, J. C.: "Effects of Distortion upon Speech and Music," Elec-
trical Engineer's Handbook, John Wiley & Sons, Inc., New York, N. Y. (1936),
Sec. 9-35. (Permission to reproduce Fig. 1 obtained from Mr. Steinberg.)

2 OLSON, H. F., AND MASSA, F. : "Applied Acoustics," P. Blackiston Son & Co.
(New York, N. Y.), p. 341.

3 FREY, H.: "Elektroakustiche Untersuchungen in Halbraumen," Franz
Deuticke (Leipzig, 1936), p. 12. (Permission to reproduce Fig. 4 obtained from
Mr. Frey.)

4 OLSON, H. F., AND MASSA, F.: "Applied Acoustics," P. Blackiston Son & Co.
(New York, N. Y.), p. 268.

INTERFERENCE EFFECTS. IN ROOMS*
M. RETTINGER**

Summary. — A discussion of interference effects in rooms, and their influence upon
syllable articulation and naturalness of reproduction. Results achieved with different
types of microphones, placement of the microphone, and acoustic treatment of the room
are discussed.

It is well known that the per cent syllable articulation in a room is
a function mainly of the reverberation time of the room and the dis-
tance between the source of sound and the position of listening, or
the position of the microphone. It is assumed here, of course, that
the noise-level in the room is low, and that pronounced echoes and
sound foci are absent. Because of this relation between per cent
articulation, reverberation, and listening distance we may also say
that the per cent syllable articulation is a function mainly of the
amount of "recorded reverberation," which is the ratio of totally
reflected to direct sound at the position of the microphone, and is
given by

R' = Z* = 16*-0«(1 - a) QrR = lologlo [i67rD*(l-a)/aS]
ED aS

where EB and ED represent the totally reflected and direct sound, re-
spectively; D, the distance between the source of sound and the
microphone; a, the average absorption coefficient of the material
in the room; and S, the total interior surface. Fig. 1 shows the varia-
tion of syllable articulation with recorded reverberation, as com-
puted by the writer from data obtained by J. C. Steinberg.1

It is seen that the per cent articulation decreases quite rapidly to a
value at which the recorded reverberation amounts to 6, after which
the slope of the curve becomes smaller. It has been found, however,
that although for best articulation the speaker should be within only
a few feet of the microphone, the quality of sound recorded in such

* Received May 20, 1937.
** RCA Manufacturing Co., Los Angeles, Calif.

635

636

M. RETTINGER

[J. S. M. P. E.

manner leaves something to be desired with medium or long-shot
motion pictures. This lack of naturalness is due to the absence of
reflected sound simulating the quality obtained in an ordinary room
when listening with two ears. It is possible, of course, at the expense
of some articulation, to place the microphone at such distance from
the speaker that reflections from the set walls lend enough acoustic
perspective to the recording to make the reproduced sound more nat-
ural. Whenever the microphone is placed at a sufficient distance
from the speaker to achieve this illusion of "presence," however, the

Record** 8.«pbW.tion =

20

FIG. 1 . Plot of per cent syllable articulation vs. recorded reverberation.

acoustic conditions of the set become at once apparent. Reflections
from the set walls set up a continually varying interference pattern
which may cause marked changes in the quality of the speaker's
voice, in that certain frequencies may be lacking and others accentu-
ated. In binaural hearing this distortion is absent, because the two
ears are located sufficiently far apart that the effect of pressure
maxima and minima is either ignored or equalized. The use of sev-
eral microphones does not improve the condition, because phase
differences become so apparent that the output voltage still, as ever,
contains the disturbing effects of the interference pattern.

If the flow of speech is not sufficiently rapid to cause continuous

Dec., 1937]

INTERFERENCE EFFECTS IN ROOMS

637

shifting of the interference pattern, some improvement can be effected
by introducing absorption in the set, as may be done by making the
set materials more transparent to sound, although this means im-
mediately that the microphone must be set back still farther in order
to achieve enough "presence."

An impracticable means of obviating the disturbing influence of the
interference pattern in a room in which prolonged sound is emitted
would consist in installing a rotating paddle which would continually
shift these partial nodes and antinodes, as experiments have shown

Frequency

Pressure-Operated Microphone
Velocity-Ribbon Microphone
Unidirectional Microphone

40 60 80 100 200 4 68 1000

FIG. 2. Loud speaker response curve of room, taken 15 feet from speaker.

that even in a large room, with steady sound coming from a loud
speaker, the output voltage can be made to undergo severe changes
of amplitude by a person walking in the room or merely moving his
arm. Another method, which is of interest only in making reverbera-
tion time measurements, would consist in employing two micro-
phones and two amplifiers, and superimposing the outputs in such
manner that phase differences have little effect; this might be ac-
complished by rectifying the outputs, and then adding.2

Olson3 has shown that partial velocity nodes and antinodes affect
the velocity microphone less violently than the corresponding partial
pressure nodes and antinodes affect the pressure-operated transmitter,

638

M. RETTINGER

[J. S. M. P. E.

due to the fact that the response of the velocity microphone is direc-
tional and the particle velocity is a vector quantity and the pressure
a scalar. Hence, improvement in quality is gained whenever it is
possible to use a velocity microphone, although, of course, complete
elimination of the interference system can not be expected, or even
realized, when the transducer is within the prescribed distance of the
velocity microphone (3 feet), since reflections from the rear obviously
are able to influence the output.

Improvement on this score is obtained by employing a unidirec-
tional microphone. Since the pressure ribbon and the velocity ribbon
in the unidirectional microphone are so close together that phase
differences become unimportant except at very high frequencies, the

Absorptive
Reflective

FIG. 3. Plan for review theater.

microphone is actuated even when a partial velocity node occurs at
the position of the velocity ribbon, since pressure and velocity maxima
and minima for the low and middle frequencies are sufficiently broad
that the corresponding partial pressure antinode can actuate the
pressure ribbon, and vice versa, when a partial pressure node occurs
at the position of the pressure ribbon. For that matter, also, the
unidirectional microphone, because of its decreased response to sound
at angles of incidence greater than 120 degrees, is of great advantage
in making loud speaker response measurements in a room, since it
accomplishes Kellogg's4 idea of placing a pressure-actuated microphone
in a wall when making loud speaker tests so as to eliminate the echo
from the wall in back of the microphone. One may therefore liken
the unidirectional microphone to a person whose capacity to ignore
unwanted sounds is somewhat impaired, standing against a wall and
hearing all sounds except those at low-intensity levels for which, in an

Dec., 1937]

INTERFERENCE EFFECTS IN ROOMS

639

amplifier, the Schottky effect becomes comparable to the induced
emf . from the transmitter.

Fig. 2 shows curves obtained by placing, first, a pressure-operated
microphone, then a velocity ribbon, and last a unidirectional micro-
phone, 15 feet from a loud speaker in a moderately live room. The
effect of the velocity microphone and that of the undirectional micro-
phone in smoothing out the response curve is clearly shown.

Experience has shown that flutes, pilasters, bold projections, and
other large irregularities of the walls of a room have decided effects
in diffusing the sound. While the interference pattern produced by a

FIG. 4. Plan for scoring stage with adjustable
panels (Warner Bros. First National Studios).

steady tone in such a room is not quite so pronounced as in a room
having flat walls, the growth and decay of a tone in a room having
corrugated walls approach more nearly the exponential law at any
one point in the room, and hence lend to such transients a certain
softness that is absent when growth and decay are beset by the
violent surges of partial nodes and antinodes. Indeed, next to a
proper reverberation characteristic, the degree of diffuse reflection in
a room may be said to be the most important factor affecting its
acoustics. Unfortunately, because of the complexity and variety of
conditions, no convenient yardstick has yet been found by which this
quantity of diffusion or dispersion of sound in a room can be measured
and directly correlated to diffusion measurements in another room.
The ratio of velocity of sound to mean free path in a room is some-
times given as a rough measure for the degree of sound mixture, but

640 M. RETTINGER [J. S. M. P. E.

does not appear to be a very convenient one, chiefly because it does
not include the phenomenon of interference in itself, but merely states
the number of reflections that will occur per second at any point in a
room if and when the sound energy flux per unit area is the same
everywhere in the room, that is, when complete diffusion already
exists in the room.

Hence, whenever good acoustics are to prevail in a room, several
properly oriented splays should be installed therein. In particular,
when reflective splays are so arranged in conjunction with absorbent
material as to reduce the time lag effects, cleaner reproduced music
and a clearer reproduced speech can be expected. The fact that such
splays may cause a larger number of "sound rays" to arrive at the

FIG. 5. Loud speaker response curve, taken near the speaker in a room
12 X 12 X 36 feet.

listener's position out of phase with the direct sound is not of great
importance, because of the rectifying action of the ear.

Fig. 3 shows the plan of a review room altered to the shape shown.
Besides using staggered reflective splays to increase the dispersion of
the sound, the walls are treated with alternate layers of hard and soft
surfaces in such manner that echoes can not occur between the walls,
a reflective surface facing an absorbent one directly across the room.
Such an arrangement allows quite a large portion of the total sound
energy to come to the auditors after a single reflection from the uni-
formly reflective splays ; thus the absorption characteristic of the re-
maining portion of the wall surfaces has less chance to introduce dis-
tortion in the acoustic perspective; that is, to make the ratio of
reflected to direct sound change with frequency.

It must again be emphasized that interference conditions for
steady sound are totally different fiom those of transient sound. In-

Dec., 1937] INTERFERENCE EFFECTS IN ROOMS 641

deed, transients may be so short that interference is completely un-
noticeable by the ear; this is particularly true of sibilants, rapid
tempo music, and noises. Then, too, since the number of pressure
maxima and minima in a room is approximately proportional to the
frequency, the high-pitched notes are less likely, whether transient
or moderately prolonged, to make one conscious of interference effects.
For steady-state conditions the effect of interference is, of course,
very pronounced. Indeed, a blindfolded person in a moderately live
room in which a single frequency is sounded is unable to tell from
what direction the sound is coming. Also, at a point of maximum

Frequenoy

FIG. 6. Loud speaker response curve, taken 30 feet from speaker in a
room 12 X 12 X 36 feet. The effect of room resonance at 80 and 160 cps.
is very clearly shown.

pressure, the sound appears very much louder when one ear is closed,
the difference in some instances amounting to 5 and more db.

In many cases it is desirable to provide some control of the acoustic
conditions in a room, for altering the reverberation time or for the
purpose of directing more reflected sound to a given place. Fig. 4
shows one way in which this may be accomplished. Four of the 5-foot
wide panels, reflective on one side and highly absorbent on the other,
are provided with hinges so that they can be swung around for the
purpose of exposing more or less absorbent area as desired.

Room resonance may also be considered from the point of view of
interference; when forced vibrations are impressed upon a three-
dimensional continuum free to vibrate, the free natural vibrations of
the system thereby excited produce interferences with the forced
vibrations. Such a condition — that is, when one or more of the lower
modes of vibration are prominently stimulated in a room the dimen-

642 M. RETTINGER

sions of which are not large in comparison with the wavelength of the
sound— precludes all possibility of achieving a diffuse state of sound
in a room, with the consequence that the Sabine- Jaeger law no
longer holds for this case.

Figs. 5 and 6 show loud speaker response curves in a room in which
the width was equal to the height (12 ft.). Fig. 5 was taken near the
loud speaker; Fig. 6, at a considerable distance from the speaker. It
is seen that when the incident sound was mostly direct sound, the
effect of room resonance could not make itself felt, but became very
pronounced farther from the speaker. Such a condition exists in
many of the smaller rooms, and is usually corrected by the introduc-
tion of suitable acoustic material and bold irregularities on the walls.

The writer takes this opportunity to express his sincere apprecia-
tion to N. Levinson and W. A. Mueller, of Warner Bros. First
National Studios, whose interest in the author's work was responsible
for many of the constructions and data mentioned in this paper.

REFERENCES

1 STEINBERG, J. C.: "Effects of Distortion on Speech and Music," Electrical
Engineer's Handbook, John Wiley & Sons, Inc. (1936), Section 9-35.

s WENTE, E. C. : "The Characteristics of Sound Transmission in Rooms,"
/. Acoust. Soc. Amer., 7 (Oct., 1935), No. 2, p. 123.

3 OLSON, H. F., AND MASSA, F.: "Applied Acoustics," Blackiston Son & Co.
(1934), p. 266.

4 KELLOGG, E. W. : "Loud Speaker Sound Pressure Measurements." J. Acoust.
Soc. Amer., 2 (Oct., 1930), No. 2, p. 157.

REPORT OF MEMBERSHIP AND SUBSCRIPTION
COMMITTEE*

Summary. — A resume of membership activities since the beginning of the year.
The growth of membership is continuing apace, and at the present time stands at its
all-time high figure.

September 30th of this year ended another period of substantial
growth of membership of the Society. Two hundred thirteen new
members have been added to the rolls since the first of the year — an
average of approximately twenty-four per month. In addition, four-
teen applications are pending.

This brought the membership, on September 30th, to a total of
1259, broken down into the following grades:

Honorary 5

Fellow 133

Active 309

Associate 812

The total would have been considerably larger were it not for the
fact that 154 members were dropped because of non-payment of dues.
Many of these will, of course, pay up during the next few weeks; in
fact, some have sent in their remittances since September 30th. We
trust that if there are any present who are in arrears, they will settle
up before the convention closes.

While the collection of dues and the follow-up of delinquent mem-
bers are not functions of the Membership Committee, the loss to
the Society of a large number of members naturally tends to counter-
act the work of the Committee, so we are now bending our efforts
toward the reinstatement of these delinquents.

The list of 154 names was broken down geographically and divided
among the members of the Committee, for direct approach by the
Committee members. It is our hope that as a result of our efforts
most of the delinquents will be reinstated.

If successful in our endeavors, our prediction is that we shall have

* Presented at the Fall, 1937, Meeting, at New York, N. Y.

643

644 MEMBERSHIP AND SUBSCRIPTION COMMITTEE

a membership of at least 1375 by the end of the year, or nearly twice
the number when our present Membership Committee took over this
work several years ago.

Subscriptions for the JOURNAL have also been coming in at a satis-
factory rate. On December 31, 1936, there were 298. One hundred
twenty -two were received during the year, making a total of 420.
Seventy-five, however, expired, making the net number 345.

The Chairman wishes to express his thanks not only to the members
of the Committee, but also to others who have assisted in the member-
ship work.

E. R. GEIB, Chairman

SYMPOSIUM ON TRANSMISSION METERS

A CONTINUOUS LEVEL RECORDER FOR ROUTINE
STUDIO AND THEATER MEASUREMENTS*

G. M. SPRAGUE AND JOHN K. MILLIARD**

Graphic records of gain-frequency and acoustical response measurements on
sound recording and reproducing equipment are normally obtained by making
measurements at sufficient points to permit drawing an average curve on ap-
propriate graph paper. Measurements made in this manner require considerable
time and equipment and become very cumbersome when numerous routine mea-
surements are necessary.

The value of an automatic device for such measurements has been recognized
for some time, and units have been developed for such work; but due to their
expense, complicated equipment, and limited application, they have not superseded
the manual methods of measurement.

In the motion picture studio, the large quantity of sound recording and repro-
ducing equipment necessitates numerous routine measurements, to insure proper
operation and maintenance of the equipment. The measurements, although re-
duced to the most practical form of daily tests, with standard test equipment, re-
quire considerable time and personnel, and, in addition, as they do not indicate
the actual response at each frequency in the operating range, introduce the
possibility of error. Recognizing the advantages of such a recorder, M-G-M
Studios have designed and constructed a unit primarily for routine tests, although
applicable to laboratory and development work also.

In making such measurements, automatically in permanent recorded form, the
fundamental units listed below are required. These units are indicated in Fig. 1.

"Send" Equipment. — (1) An audio-frequency oscillator, of the beat-frequency
type with a frequency range of at least 20 to 10,000 cps. and with a constant out-
put level over this frequency range; appropriate matching and attenuating net-
works, level indicator, and output controls.

(2) Automatic drive (frequency variation) for the oscillator, with frequency
indicating device, and also a warble unit if acoustic measurements are desired.

"Receive" Equipment. — (1) A bridging amplifier for measurements, without
disturbing operating equipment ; a preamplifier for low-level measurements from
microphone output, etc.

(2) A rectifier, linear or logarithmic, for conversion of input audio frequency
to direct current for operation of the recording device.

(5) A direct-current amplifier.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received May
21, 1937.

** Metro-Goldwyn-Mayer Studios, Culver City, Calif.

645

646

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. p. E.

(4) A graphic recorder: Esterline-Angus recording milliammeter — 0 to 5 ma.
A detailed description of the equipment follows:

"SEND" APPARATUS

Beat Frequency Oscillator. — The beat frequency oscillator, as well as the remain-
der of the apparatus, was designed for standard rack mounting. The oscillator is
in three units: the radio-frequency oscillator and detector unit are mounted on a
12x/4 X 19-inch panel; the audio-frequency amplifier, volume indicator, output
impedance control and frequency standard reeds, on an 83/4 X 19-inch panel;
and the power supply on a 7 X 19-inch panel, making an overall panel size of
28 X 19 inches.

As an oscillator of constant output, over the range of 20 to 14,000 cps., was

FIG. 1. Diagram of automatic recorder.

required, it was necessary to develop such a unit. The maximum deviation from
the 1000-cycle output level is 0.2 db. in the present unit. The output at 10
cycles is down 4 db. from the 1000-cycle output level. The frequency range of 20
to 14,000 cps. is covered by a dial length of 14 inches. In order to make this unit
a multi-purpose oscillator, it was necessary to use a multiple-winding output
transformer.

The use of this transformer necessitated the addition of an audio-frequency
equalizer to compensate for the reduction in low-frequency output in the trans-
former ( —2 db. at 20 cps.). The range of output impedance is from 2l/2 to 500
ohms in 11 steps.

The oscillator unit contains the output control (RF input to detector), with
a useful range of 25 db. The audio amplifier unit contains a step control cali-
brated for 0.02-0.2-2.0 watts' output. This oscillator was designed for a normal
channel plate supply voltage of 350. The filament supply is alternating current.

Dec., 1937] SYMPOSIUM ON TRANSMISSION METERS 647

On the 500-ohm output tap, into a load of 500 ohms, the harmonic content at
1000 cps. is as follows:

Db. Out 3rd Harmonic 2nd Harmonic

(Per Cent) (Per Cent)
0 0.02

+ 10 0.05 0.03

+20 0.11 0.12

+24 0.27 0.25

The frequency stability is high. A change in the 350-volt supply of ±30 volts
changes the frequency 2 cps. at 500 cps., or approximately J/2 per cent.

The oscillator is a fixed -frequency oscillator at 94 kilocycles, and is electron
coupled-resistance stabilized, using a 36 type of tube. The variable-frequency
RF oscillator, 80-94 kilocycles, uses a similar tube and circuit. A band-pass
filter is used in the variable-frequency oscillator output. Although not required
for sinusoidal output, it was found helpful in controlling the overall output charac-
teristic of the unit. The two RF oscillators may be operated at the same fre-
quency (zero-frequency output) without tendency toward interlocking.

The detector unit is push-pull, employing two WE-262A tubes operated as
full-wave square-law rectifiers. These tubes are not efficient as detectors but were
selected for their low microphonic output.

Spurious beat notes are entirely eliminated by a 3-section, 40-kc cut-off,
low-pass filter in the detector plate circuit. The minimum level difference be-
tween oscillators, at the detector input, is 20 db.

The audio-frequency amplifier is a 3-stage push-pull, resistance-coupled
unit, with a gain of 60 db. The first two stages use WE- 26 2 A tubes and the out-
put stage WE-271A tubes. These tubes were selected for their low microphonic
and hum levels.

A volume indicator with a range of —10 to +30 db., in 4-db. steps, is normally
across the amplifier output.

For calibration, two reeds are used, operated by a phonograph pick-up switched
across the amplifier output. The primary reed is tuned to 118 cps. and the
secondary reed to 475 cps. The calibration control is a 60 ppf variable condenser
in the fixed-frequency RF oscillator circuit, with an 80 to 1 gear control. Pro-
vision was made for indication of zero beat in the detector plate circuit, but, due to
the low detection efficiency of the 262 A tubes, this meter was not included in the
final assembly.

Drive Control. — A novel method of drive and warble control is employed. The
oscillator frequency control is driven by a rack and pinion, engaged by a cone fric-
tion clutch to a small driving motor. This drive has an adjustable speed, cover-
ing the range of 20 to 14,000 cps. in a minimum time of 35 seconds and adjustable
for any intermediate time up to 1 minute, 45 seconds. Control is by rheostat in
the motor circuit. The frame or stator of the driving motor is suspended in a
cradle and is free to move through an angle of 5 degrees.

A short arm, connected to the motor stator, is held in contact with a cam by
spring tension. This cam is mounted on the rotor of a second small motor, the
stator or frame of which is secured to the panel (see Fig. 2). The driving motor
is then oscillated by the second motor, at a rate of 7x/2 cps. This oscillating mo-

648 SYMPOSIUM ON TRANSMISSION METERS [J. S. M. P. E.

tion is transmitted to the rotor of the driving motor and results in a like motion of
the driving rack, and consequently, the oscillator frequency control dial. The
warble is approximately 5 per cent at 100 cps.; 4 per cent at 1000 cps. and I1/:
per cent at 10,000 cps. It may be switched on or off at any instant, during the
steady drive period, or while the oscillator is fixed at one frequency. The motors
are small a-c. geared induction motors. The cam arrangement on the warble
drive is removable for changes in the rate of warble. The drive control panel is
7 X 19 inches in size.

After completing the sweep to 14,000 cps., the drive and warble motors are
automatically stopped by means of a cut-out switch operated from the drive rack.
Manual reset requires only a fractional turn of the drive clutch for release and
turning the oscillator dial back to the desired starting frequency. Again, spinning

FIG. 2. Drive and warble unit.

in the cone clutch knob engages the drive and the oscillator frequency is again
varied, without necessitating turning the drive motors off and on manually.

Frequency Indicator.— Frequency indication during this automatic sweep is
by two methods. On the back of the oscillator frequency dial are placed 16
small adjustable L-shaped contactors. These contactors operate a single-pole,
single-throw switch, mounted behind the dial, as each contactor passes the
switch. Contactors are placed at 30, 50, 100, 200, 300, 500, 1000, and at each
thousand cycles up to and including 10,000 cps.

Due to the inclusion of the warble feature in the drive system, a simple switch-
ing circuit could not be used for frequency indication, as the backward and for-
ward movements of the dial caused a minimum of four operations of the switch
in approaching the indicating frequency, and a similar number when leaving this
frequency. Also a slow operating indicator, necessarily used to interrupt the
frequency for indication, would remove too large a section of the frequency band
for most measurements. A time-delay impulse relay is used. This relay circuit
was designed to be inoperative during the unavoidable impulses due to warble

Dec., 1937] SYMPOSIUM ON TRANSMISSION METERS 649

operation, and operative for the small time intervals between frequency-indicating
periods at -high-speed drive. The frequency indication is by means of a mo-
mentary shorting switch on the oscillator amplifier output circuit. This causes a
dip in the output and results in a 2-db. reduction as indicated on a high-speed
volume indicator meter. The duration of the short-circuit is 0.07 second, and on
the high-speed drive it causes a gap of 14 cycles at 1000 cps. The frequency-in-
dicating device is also equipped to operate a second relay for frequency indication
on the graphic recorder. This relay punches a small hole in the paper at the in-
dicating frequency.

Both indicating relays may operate simultaneously or individually, and fre-
quency indication may also be by manual operation of the control key, making
possible indication at any desired frequency.

The time-delay impulse relay indicating unit is self-contained, a-c. operated, and
is mounted on a 7 X 19-inch panel. An a-c. power panel with main switch and
fuses is used to turn all equipment on and off.

A series of H pads is supplied for level control and impedance matching, and a
jack row provides flexibility, permitting any desired combination of output units.

The entire "send" equipment mounts on a standard rack, requiring 56 inches of
panel space. The unit is shown in Fig. 3, and is the bay on the right side. The
equipment from top to bottom is as follows: (1) equalizer and H pads; (2) jack
row; (5) beat-frequency oscillator, including AF amplifier, oscillator-detector unit,
and oscillator power supply; (4) drive control panel; (5) frequency indicator
panel; (6) a-c. power panel.

"RECEIVE" APPARATUS

The second or left-hand rack in Fig. 3 contains the "Receive" equipment. A
detailed description of this apparatus follows :

AF Amplifiers. — Two amplifiers are supplied, one a bridging amplifier, per-
mitting recording from operating circuits, and the other a preamplifier to permit
operation directly from a microphone. The bridging amplifier has a gain of 14 db.
(bridging 250 ohms.) ; a frequency characteristic flat within ± Vio db. from 20 to
10,000 cps.; a gain control of 20 db. in 2-db. steps. Two 6C5 tubes are used in
push-pull, the plate supply is 350 volts, and the filament a-c. At the normal maxi-
mum output level of +10 db. there is Vio per cent third harmonic at 1000 cps.
This amplifier is mounted on a 3*/2 X 19-inch panel.

The preamplifier operates between 200 and 500 ohms, has a maximum gain of
88 db. and a gain control of 70 db. in 3/4-db. steps. The frequency characteristic
is flat within ± l/4 db. from 20 to 10,000 cps., and at the normal maximum operat-
ing output level of — 4 db. the second harmonic is V< per cent of the fundamental
1000 cps. The combination of the two amplifiers makes available a maximum
gain of 102 db. and permits recorder operation from an input of —92 db.

The preamplifier uses one 6F5 tube and two 6C5 tubes, resistance coupled. The
plate supply is 350 volts and the filament supply a-c. This amplifier mounts on a
7 X 19-inch panel.

Rectifiers. — The preceding amplifiers feed into either a logarithmic or linear
rectifier circuit. The linear rectifier is used for measurements requiring maximum
accuracy. The useful range is 25 db., and the indications may be read most ac-

650 SYMPOSIUM ON TRANSMISSION METERS [J. S. M. P. E.

curately at peak levels where a variation of Vio db. is easily discernible. This
linear rectifier consists of a full-wave rectifier using a 6H6 tube. A single-section
low-pass filter is used. The unit is linear over a 30-db. range and the frequency
characteristic is flat within =*= Vio db. from 20 to 10,000 cps. The peak output cur-
rent required is 6 ma., and the output voltage 3 volts at the load resistor of 500
ohms.

The alternate rectifier is of the logarithmic type. It covers a range of 45 db. in
true logarithmic manner, and the frequency response is flat within =*=0.2 db. from

FIG. 3. Continuous level recorder.

20 to 10,000 cps. In this type of rectifier the transformation of volts or milli-
amperes to db. is automatically made in the rectifier unit, with the result that uni-
form level changes, in db. at the input, produce uniform current or voltage changes
at the output. The graphic recorder is a milliammeter, necessitating converting
to decibels the indications recorded with the linear rectifier. This manual con-
version is not required when using the logarithmic rectifier. In this unit each
division of the 50-division paper (over a range of 45 db.) indicates 1-db. change in

Dec., 1937] SYMPOSIUM ON TRANSMISSION METERS 651

input level. The direct-reading feature, plus the increased range, makes possible
many measurements involving large level changes not conveniently made with the
linear rectifier. The logarithmic rectifier uses two 6F5 tubes as drivers, two 956
tubes as log amplifiers, and one 6H6 tube as linear rectifier. The 956 tubes are
of the variable-mu type in which the relation between mutual conductance and
grid voltage is logarithmic over a considerable portion of the operating range. By
proper selection of circuit constants these tubes amplify the input negative half-
cycles in a logarithmic manner, so that the output voltage is proportional to the
logarithm of the input grid voltage. The 965 output is rectified by a half-wave
6H6 rectifier, passed through a low-pass filter, appearing as a d-c. voltage at the
output circuit. The approximate logarithmic range of a single 956 tube, as used,
is 15 db. By suitably combining the output of two of these tubes in a parallel cir-
cuit, the range may be extended to 45 db. In order to secure the 45 db. range,
over the frequency band of 20 to 10,000 cps. and with an error not exceeding
0.25 db., equalization in the 956 plate circuits is necessary. This equalization
necessitates pre-equalization of the overall unit for linear frequency response.

Due to the inherent frequency error in logarithmic rectifiers of the preceding
type, the replacement unit will employ a fixed-frequency oscillator exciting
the logarithmic rectifier. This oscillator will then be modulated in a linear manner
by the operating audio input. By this method a true logarithmic range of 60
db., the practical limit set by the graphic recorder, with negligible frequency and
amplitude distortion, will be obtained in a stable compact unit.

The plate supply of the present unit is 350 volts and the filament supply is a-c.
This unit mounts on an 83A X 19-inch panel.

D-C. Amplifier. — The next unit in the series is the linear direct-current ampli-
fier. This amplifier uses a 6C5 and a 6F6 tube. The plate supply is 350 volts
and the filament supply is a-c. This amplifier is linear over a range considerably
greater than the graphic recorder demands. The recorder requires 5 ma. for full-
scale deflection, making a 10-ma. output necessary at the d-c. amplifier due to
the bridge output circuit used. This amplifier is very stable; a change of ±15
volts in the 350-volt plate supply causes no change in operating characteristics.
It works into the 500-ohm load of the graphic recorder.

The d-c. amplifier input voltage necessary for the peak indication of the recorder
is 3 volts. The accuracy over the entire range is 0.02 db. This unit is provided
with a 3-position input key, selecting the logarithmic or the linear rectifier
output, the third position being for calibration (zero adjustment).

In normal operation, using the linear rectifier, the recorded chart reads from
right to left, or backward, with respect to accepted methods of reading. To
correct this defect, the logarithmic rectifier is so designed that for no input the
recorder deflection is maximum (5 ma.). Increasing input causes a reduction in
this indication, producing a completed graph reading from left to right, in the
normal manner. The present logarithmic rectifier, designed for 50-division paper,
produces a deflection of one division for each decibel of input, resulting in an easily
readable graph.

The linear rectifier record must, of course, be translated by the standard method
(20 logio ratio of currents). This rectifier necessarily compresses the record as the
level decreases. While such a record is not conventional, compared to present
records in decibels, its accuracy is high and a minimum of equipment is required.

652

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. p. E.

Familiarity in reading records of this type is readily acquired.

Fig. 4 is a frequency response curve of a standard recording channel, with a
7500-cps. cut-off low-pass filter. This record was made with the linear rectifier.
In Fig. 5 is the same measurement using the logarithmic rectifier. Both measure-
ments were made at high speed in order to reduce the size of the graph. Note
the frequency indications made by the shorting relay, described previously.

Graphic Recorder.- — The recorder used in this installation is an Esterline-Angus
recording milliammeter, with a full-scale deflection of 5 ma. and a resistance of
500 ohms. The unit is very rugged and reliable, and relatively inexpensive. It
is not normally used for high-speed recording, and requires minor modifications
for this work.

The recorder, as adjusted, has a maximum recording speed of 80 db. per second
when used with the logarithmic rectifier of 60-db. range. The recording needle

— /

FIG. 4. Frequency characteristic made with linear rectifier.

completes the 9-inch travel across the paper, and back to zero again, in I1/! sec-
onds.

The meter movement is very rugged, and withstands overloads of several
hundred per cent. The ink-well holds one ounce, a supply sufficient for several
days of normal recording. A siphon supplies the glass recorder pen with ink.
The pen will remain in contact with the paper for all but extremely high-speed,
high-level impulses, not encountered in normal recording.

The drive is a synchronous motor. The range of paper speed is from a maximum
of 12 inches per minute to a minimum of 3/« inch per hour, with the standard
gears supplied. The chart paper is supplied in standard 90-foot rolls, and is 6
inches wide with a recording width of 4]/2 inches. Recordings roll up on a take-up
roller exerting a uniform tension on the paper.

The frequency indicating punch, previously mentioned, is a small impulse relay
operated from the time-delay relay unit in the oscillator bay. This relay when
operated, makes a pin-point hole at the instant of operation in the arc of pen travel,
at the edge of the paper. This punch, interlocked with the oscillator drive, thus
makes a permanent record of frequency vs. response. Pencil notations, as to
frequency, etc., may easily be made directly upon the chart during operation.

Dec., 1937]

SYMPOSIUM ON TRANSMISSION METERS

653

The recording milliammeter is 13 inches high, 8Vz wide, and 91/: deep, and is
mounted on a 14 X 19-inch control panel (see Fig. 6).

This panel contains the motor drive key and also an input key, which transfers
the d-c. amplifier output to the recording milliammeter or to a standard 301 type,
5-ma. meter in a 500-ohm circuit. This meter is used for all preliminary adjust-
ments, as its scale is similar to the recording milliammeter scale. The recording
milliammeter is fused with Vs-ampere "littlefuses."

The 350-volt plate supply and the a-c. filament supply for all units in the re-
corder bay is from a power supply unit mounted on a 7 X 19-inch panel.

The a-c. power panel at the bottom of the bay contains the a-c. line switch
and fuses, and a Variac and a-c. voltmeter, which also may be patched to the
oscillator bay for regulation of the a-c. input voltage to the normal 120- volt value.
This control is required when field measurements are made, as the a-c. line voltage
is frequently below 100 volts.

FREQUENCY CHARACTERISTIC

FIG. 5. Frequency characteristic made with logarithmic rectifier.

A standard rectifier type of volume indicator is also included, at the top of the
bay. This unit has a range of —10 to +30 db., and when used with the pre-
amplifier and bridging amplifier, forms a standard acoustic meter. The volume
indicator is normally used with the graphic recorder for preliminary level adjust-
ments.

The recording unit has been designed for a + 10-db. output level at the bridging
amplifier for full-scale deflection of the recording milliammeter, with the linear
rectifier. This level is sufficiently low to permit economical amplifier design, and
high enough to prevent trouble from pick-up.

Further refinement of equipment is unnecessary, due to the limitations of the
recording milliammeter. The hysteresis inherent in a medium priced instrument
of this type is of the order of J/2 per cent of full-scale deflection. The recorder
bay has 56 inches of panel space. Patchable equipment appears at the jack row,
below the volume indicator panel.

In Fig. 3 the equipment from top to bottom (left-hand rack) is as follows: (1)
volume indicator; (2) jack row; (5) preamplifier; (4) graphic recorder; (5)

654

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. p. E.

logarithmic rectifier; (6) bridging amplifier; (7) linear rectifier; (8) d-c. amplifier;
(9) power supply; (10) a-c. power panel.

All equipment has been constructed as compactly as possible for practical
operation and maintenance. The two bays are rigidly mounted upon a wheeled
base for rapid transportation. Microphonic response is negligible in the unit.
The only source of supply necessary is 110 volts B0/eo-cycle a-c. The power con-
sumption of the entire unit is 350 watts.

FIG. 6. Graphic recorder.

The assembly is very flexible and individual units are available, thus not con-
fining the unit strictly to graphic recording.

The recording unit may be used also for reverberation measurements, using the
60-db. logarithmic rectifier. With increased speed of the synchronous chart drive,
the exciting frequency may be interrupted and the decaying sound impulse re-
corded. The recorded chart of sound intensity vs. time, over a 60-db. range, may
then be used to indicate reverberation time. This makes a complicated timing
device unnecessary for normal reverberation period measurements.

Dec., 1937] SYMPOSIUM ON TRANSMISSION METERS 655

The conception of this unit and its development into a practical transmission
meter was by J. K. Hilliard, Transmission Engineer; the design and construction of
the automatic recording unit was under the direction of G. M. Sprague, Engineer,
and the new type of drive and warble unit was developed by O. L. Dupy, Re-
cording Engineer, all of the Sound Department, M-G-M Studios.

This equipment has proved a very valuable tool in the measurement of filters,
equalizers, calibration of microphones, acoustic response of loud speakers, and in
the standardization of review rooms. The characteristics of prints, printers, and
noise and signal components from film have also been studied at length to great
advantage.

A CURVE-PLOTTING TRANSMISSION METER'
L. A. AICHOLTZ**

The most important feature of the transmission recording meter described here
is the compressor circuit. Fig. 1 shows the complete measuring system, com-
prising an oscillator, at the center, the compressor circuit at the left, and the re-
cording meter at the right. The object next to the meter is a device made to hold
a 630 microphone and either a 705 or D -9768 9 Western Electric headphone for
making routine microphone and headphone measurements.

The oscillator is an RCA serviceman's oscillator, with a few refinements and a
new panel which mounts the synchronous motor drive and other accessories. The
recording meter is an Esterline Angus recording milliammeter, also with syn-
chronous motor drive.

The purpose of the compressor circuit (Fig. 2) is to obtain a current in the re-
cording meter having a straight-line relationship in decibels to the input signal. If
for this purpose we employ a vacuum tube V2 having its input circuit arranged like
the familiar grid-leak-and-condenser detector, the bias for this tube, normally at
zero, will increase negatively for any input signal, up to a value that is approxi-
mately equal to the positive peak value of the input signal, and the plate current
will decrease accordingly. Fig. 3 shows that for minimum signal the plate cur-
rent is maximum.

If, then, the tube used has a grid voltage-plate current characteristic that is
logarithmic, the change of d-c. plate current will bear the desired relation to the
a-c. signal. The best vacuum tubes available for this purpose are the so-called
"super control" or variable-mu tubes, such as the RCA type 58. If one such tube
is used in position Vz the input signal-output characteristic will be as shown by
curve OA of Fig. 3. Note that this curve is reasonably straight over a range of
10 or 12 decibels. However, a much greater range is desired, and it is possible
to employ a second tube for this purpose, so connected as to place its response
curve at the position BD. The departures from linearity of the two tubes are

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
18, 1937.

** Universal Studios, Universal City, Calif.

656

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. P. E.

then nearly balanced out, and we obtain the long and more or less straight
curve OC.

Referring to Fig. 2, this is accomplished by V3, whose plate current also passes

FIG. 1. Complete measuring set-up.

through the recording meter. Its input signal is kept small compared to that of
Vj, so that it does not contribute any reduction of the total plate current until
the signal voltage is high enough to reach the knee of curve OA . The input signal
of Vt is controlled by the "overlap" adjustment.

FIG. 2. Compressor circuit.

The unwanted steepness of the upper part of OC (Fig. 3) results from the con-
tinued slight rise of OA beyond the point of overlap. Compensation is attained
by introducing a resistance in the plate circuit of V$ which we call a "slope" ad-
justment, and which causes this second tube to contribute proportionately less

Dec., 1937]

SYMPOSIUM ON TRANSMISSION METERS

657

as the signal voltage rises. The resulting overall curve OD is the experimental
calibration of the instrument. When these two adjustments are at their optimum,
the instrument provides a linear response over a 30-db. range. The slope adjust-
ment resistance is in the portion of the plate circuits common to V3 and V^ (Fig. 2).

FIG. 3. Calibration of compressor circuit.

As mentioned above the device responds to the peak value of input signal. In
cases where the signal wave-form is asymmetrical the meter response will be dif-
ferent according to the poling of the various circuits under test. To avoid errors
that might inadvertantly arise from such cause, the circuit is made symmetrical
by adding V* and F6 in push-pull relationship to F2 and V3.

FIG. 4. Meter calibrations and response in 10-db.Jsteps.

Other features of the circuit include a visually read panel meter in series with
the recording meter; a substitute resistance to keep the visual meter sensitivity
standard when the recording meter is out of circuit ; a doubling shunt to protect
the visual meter during line-up; a common sensitivity adjustment for both meters;
an adjustable biasing current common to both meters, to adjust the meters to

658

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. P. E.

Transmission Characterlstl
Jl»» I.E. 705-i neadsetf
courled to 630-A mlcropli

— \ A — - — "V^

\ Tr«nsml3«lon Characteristic Z^V „ _7\_.

_"_\ your W.B. 630-A nlcrorhon«« A \ —

\ coupl*d to D-97689 headset \ \-

FIG. 5 ( Upper") . Transmission characteristics of headsets.
FIG. 6 (Center). Effect of coupling between headset and

microphone.

FIG. 7 (Lower). Transmission characteristics of micro-
phones.

Dec., 1937]

SYMPOSIUM ON TRANSMISSION METERS

659

full scale for zero signal; and a large-capacity shunt condenser may be inserted
across both meters in order to obtain a partially integrated result with a rapid
sweep frequency when making acoustic measurements. This integration ac-
complishes much the same result in avoiding standing- wave patterns as would a
warble tone at discrete frequencies.

Fig. 4 shows the meter calibration, and also the response in 10-db. steps, of
which 3 steps are linear. To demonstrate some of the duties performed by this
meter, Fig. 5 shows a series of curves run on five 705 Western Electric headphones,
the first four being regarded as normal, while the fifth, due to rough handling,
is obviously defective.

The measurements were made by placing the headphone in close contact with a
Western Electric 630- A microphone, and sealed with a rubber coupling approxi-

FIG. 8. Acoustic curves of (A , lower) review room and (B, upper) Pan-
tages Hollywood Theater.

mately J/2 inch thick. The device to hold headphone and microphone for these
curves is shown in Fig. 1 next to the recording meter.

Fig. 6 shows the effect of air leakage when the rubber seal between the head-
phone and microphone is omitted.

Fig. 7 is a comparison of several 630-A microphones using the seal between
microphone and headphone. We also find this equipment very useful in balancing
the acoustic characteristics of review rooms.

Curve A of Fig. 8 shows an acoustic run in our review room No. 7. This was
made by placing a microphone near the rear of the theater, and from a con-
tinuous frequency film run on the projector a chart of the acoustic output was
made on the recording meter.

Pantages Theater in Hollywood is now being used as our yard-stick for sound

660 SYMPOSIUM ON TRANSMISSION METERS [J. S. M. P. E.

quality, and curve B (Fig. 8) shows the acoustic run made in the 26th row center
of the main floor. This curve is l/6 longer than curve A, due to the fact that the
recording meter motor was operated on 50-cycle supply for curve A and 60-cycle
for curve B. An integrating condenser of 50 nf was used in each case.

These runs are not intended to prove or disprove any theory about the char-
acteristic of headphones, microphones, or theaters, but are intended as means of
making routine checks of equipment and to correlate listening tests with actual
measurements.

A CURVE-PLOTTING TRANSMISSION METER*

L. D. GRIGNON**

The need for a curve-plotting transmission meter has frequently been felt by
every engineer in acoustics and transmission work, but up to the present the
available meters have had very definite limitations as to characteristics or price.
Following is a description of a meter constructed at a reasonable cost and having
certain desirable characteristics.

One great advantage of a curve-plotting transmission meter is the saving of
time effected when a great many measurements are to be made, such as tests of
various circuits or circuit combinations, acoustic runs at various points in a room,
or routine tests of many individual pieces of equipment. In deciding upon the
requirements of such a meter it is apparent that a linear decibel scale should be
used, and, further, the frequency coordinate should be logarithmic; in other words,
coordinates similar to those of the semi-log plotting paper used by engineers for
plotting transmission characteristics. Having such a set of coordinates, prelimi-
nary inspection of curves may be made without resorting to a transparent cali-
brating scale. This practice would not be strictly necessary if paper rolls having
a frequency scale printed thereon were readily available, and provided that some
such scale could satisfactorily be made standard by the users of similar meters.

Oscillator Drive. — A Western Electric 13- A oscillator being the only one avail-
able at the moment, a design was produced wherein a small motor of VTO hp.
drives the oscillator condenser through a gear reduction system, a friction wheel,
and an odd-shaped cam to convert the angular frequency scale of the oscillator
to a frequency scale that is logarithmic with respect to time. The gear ratio and
chart speeds were selected to obtain a scale the length of a piece of Codex No. 3115
semi-log plotting paper. The gear reduction system consists of one set of worm
gears and one set of bevel gears having ratios of 80:1 and 4:1, respectively, or a
total reduction of 320:1, placed in a duralumin housing. A long spring provides
a minimum of pressure against the cam where pressure is least needed and in-
creases the pressure as the friction wheel arrives at the smaller cam radii. The
approximate cam design was obtained by computation and graphical methods,
and the cam was then cut slightly larger than the calculated dimensions. By

* Presented at the Spring, 1937, Meeting at Hollywood Calif. ; received May
21, 1937.

** Paramount Pictures, Inc., Hollywood, Calif.

Dec., 1937]

SYMPOSIUM ON TRANSMISSION METERS

661

running the meter and oscillator drive, and marking the chart at appropriate
frequencies as the oscillator passed them, the corrections to the cam were deter-
mined and the cam trimmed down to the final shape by the cut-and-try process.
This non-technical method was used because of unavoidable inaccuracy in the
graphical solution over parts of the frequency scale where the change is very
great. Computation is difficult because of the necessity of considering the arc
or point of contact of the friction wheel. After the final cam shape was obtained
a checkering file was used on the edge to give a better grip for the friction wheel.
The friction wheel is a medium-hard rubber hub between two metal washers
which act as positive guides. The greatest tendency to slip occurs at frequen-
cies from 5000 to 9500 cps., which is the highest frequency used; but except when
the wear of the friction wheel is excessive, the reproducibility of the frequency

FIG. 1.

Curve-plotting meter and oscillator drive, on Western Electric
13- A oscillator, for frequency scale.

scale is within l/& inch out of 7/8. The complete meter is shown is Fig. 1,
wherein the oscillator drive is easily seen.

Conversion Amplifier .—The. available chart-plotting meter being a current-op-
erated device, it was necessary to have an amplifier that would produce equal in-
crements of current at its output for each decibel change of input. In such a
conversion amplifier practicable limits of linearity normally exist. In the ampli-
fier to be described, linearity within =*=0.1 db. is maintained over a range of 12
db. Over a 20-db. range there is a deviation from linearity of approximately 1
db. at each end.

Fig. 2 is the schematic circuit of the amplifier, which consists of a type 76 tube
used as amplifier, another 76 used as half -wave rectifier, and a 6D6 as a d-c. relay

662

SYMPOSIUM ON TRANSMISSION METERS [J. s. M. P. E.

tube. The filter network connecting the diode to the 6D6 grid may be arranged
for various amounts of time delay, the values of which depend upon the measure-
ments being made. The operating point of the relay tube is selected by means of
Pa. Pa is a shunt around the meter to reduce the current increment through the
meter per decibel to conform to 1 db. per division on the chart being used. P«
controls the mid-range position on the chart. In this particular instrument zero
level (0.066 watt) is adjusted to mid-scale of the chart. Both Pa and P4 have
switches incorporated for opening the potentiometers to facilitate calibration.
As can be seen, the amplifier contains a power supply for all voltages. The vari-
ous controls for the amplifier and motors are to the left of the meter in Fig. 1.

Warble Frequency Device. — This device is used to vary continuously the fre-
quency being measured above and below its nominal value, to decrease the stand-

FIG. 2. — Schematic diagram of the amplifier.

ing-wave pattern when making acoustic measurements. This warble is produced
by a separate motor driving a balanced variable condenser, through a reduction
gear, at about 400 rpm. Another condenser, variable from the front panel, is
connected in series with the motor-driven capacity for adjusting the amount of
warble, and the combination is connected into the fixed section of the Western
Electric 13 -A oscillator.

For acoustic measurements, the transmission meter described is used for com-
parative work only, since no facilities for calibrating a microphone are readily
available. For routine transmission measurements, where the frequency char-
acteristic is within the linear limits of the amplifier, and for studies of the char-
acteristic for various circuit changes, the meter is a great time-saver. The rec-
ord produced! being an inked line, is durable and may readily be filed for future
reference.

Dec., 1937] SYMPOSIUM ON TRANSMISSION METERS 663

AN AUTOMATIC AUDIO-FREQUENCY GRAPHIC RECORDER*

A. D. MACLEOD**

In designing and engineering equipment to be used for recording and reproduc-
ing speech and music there are many different problems. Of these, the most
neglected is the measurement of the electrical to mechanical translation. It is
quite common to find a radio set manufacturer, for example, who produces a
large number of receivers, testing and checking them as far as the voice-coil of
the reproducer, but neglecting the acoustical measurements of the cone. Sound-
pressure measurements that are made are, in general, rather limited. In reality,
these measurements are of great importance to the manufacturer, as acoustical
fidelity is probably an important factor in the public's acceptance of a receiver.
Perhaps the reason why more acoustical measurements are not made is that the
time involved is too great. It was this problem that prompted development of
the Audi-0-Graph (Fig. 1), a self-contained unit that enables an overall fidelity
curve to be taken in approximately two minutes.

After setting up the tentative design features, it was found advisable to make
the equipment adaptable to as many kinds of audio-frequency measurements as
possible without limiting its usefullness for specific service. The result was a
unit that could be used for comparing loud speakers, microphones, audio ampli-
fiers, and filters. It was found necessary, for the radio manufacturers, to include
a small signal generator which could be modulated over the audio spectrum to
obtain an overall curve without tying up the use of a standard signal generator.
The unit, from a production engineering standpoint, is extremely valuable, as
changes in any part of a particular system can be readily checked for comparison
with the original set-up. Although it is possible to make all the measurements
mentioned above by other methods, the time required for setting up the apparatus
is usually as great as that required to make the measurements.

There has long been a need for an instrument that would record transmission
level in some permanent form, while automatically sweeping the audio spectrum.
The art is well acquainted with motor-driven oscillators and hand-operated re-
corders, but automatic curve-tracers, while used in a few laboratories, have not
been generally found satisfactory. Various methods have been tried, but most
of them possess disadvantages that overbalance any possible advantage from
the standpoint of automatic recording.

The problem was to develop a recorder that would handle changes up to 40
db. per second, produce a permanent ink record, be of rugged construction, and
sweep the audio spectrum while recording the level of the system under test.
The components of the complete unit should consist of an audio oscillator, a
microphone amplifier, a rectifier-control amplifier, and recorder of the control-
motor-driven type.

* Presented at the Spring, 1937. Meeting at Hollywood, Calif. ; received June
10, 1937.

** Tobe Deutschmarin Corp., Canton, Mass.

664

SYMPOSIUM ON TRANSMISSION METERS [J. S. M. p. E.

OSCILLATOR

The audio oscillator was designed so that two separate tuning condensers would
be used for manual and automatic control, switching from one to the other as
desired. The condenser for automatic control is fastened directly to the shaft
of the recording drum. The plates are so shaped that the low frequencies up to
100 cps. are spread out on the curve sheet, and above 100 cps. the scale is approxi-
mately logarithmic. This arrangement shows the cone resonance of a loud
speaker readily, and allows comparison of the finished curve with any standard
curve of the log-scale type. Fig. 2 shows a typical curve. Since the instrument
was to cover a number of applications it was necessary to provide output imped-
ances in several steps, from 50 to 5000 ohms, selected by a switch. A small os-
cilloscope is provided in the unit for checking the frequency against the 60-cycle
supply.

The output level of the oscillator was held fairly low, because the increased
output tube capacity and the associated power supply developed more heat,
which increased the problem of stability in the beat-frequency oscillator. De-

FIG. 1 The Audi-O-Graph.

generation in the audio amplifier was found necessary to hold the level within
Va db. over the recording range of 30 to 12,000 cps.

MICROPHONE AMPLIFIER

The amplifier used to produce sufficient gam to operate the control tubes of the
recorder is more or less of the conventional design, using high-gain pentode stages,
resistance-coupled and heavily by-passed. The amplifier contains also any com-
pensation necessary for the microphone used in sound pressure measurements.
A manually operated, calibrated attenuator, having 20 steps of 2 db. each, is
connected in the grid circuit of the second stage. This controls the deflection of
the recorder arm to position the graph upon the paper. The automatic attenuator
of the recorder is connected in the grid circuit of the last stage, and controls the
input to the rectifier-control amplifier, holding it to a constant value. As this
type of amplifier and recorder-control produces amplitude variations that are
linear with decibel changes of the input, it was not necessary to resort to the log-
arithmic type of amplifier as used with linear-voltage recording systems. For
the range covered by the A udi-0-Graph a logarithmic amplifier would be com-
plex and necessitate considerable adjustment at each set-up.

Dec., 1937]

SYMPOSIUM ON TRANSMISSION METERS

665

RECTIFIER

The problem of rectifying the audio input to the recorder was found to be very
interesting and more complex than was anticipated when work was first begun.
We soon learned that if the rectifier output were to be filtered to any great extent,
the recording speed of the pen would be greatly reduced. At that stage of the
development it became necessary to ascertain the required recording speed of the
various systems that the unit was to measure. A large number of speaker curves,
taken by the Bostwick method and carefully checked, revealed that a speed of
15 db. per second would cover all transitions in speaker curves. After a number of
measurements on audio amplifiers and filters it was found that at 25 db. per second
one could plot the curve of practically any system that might be encountered.
As work progressed on the recorder, speeds up to 40 db. per second were found to
be reasonable and accurate enough to be retraced several times with a deviation
of less than one step of the attenuator, which in the case of the audio unit is 0.5

" *•« V^Y^

\

FIG. 2. Curve of 6-inch permanent-magnet dynamic loud speaker, taken at

high speed.

db. Using full-wave rectification enabled us to produce a filter for the double-
frequency component that would remove the chatter from the dynamic relay
and still allow maximum recording speed. The output of the rectifier was fed
through an elaborate filter system to a high-conversion d-c. amplifier operating
the dynamic relay.

RECORDER

The first step in designing the recorder was to decide the size of the graph sheet.
Shortly after work was started upon the recorder it was found that the greater
the length of the sheet could be made the more accurately changes could be re-
corded. The length finally decided upon was one that would fold double into a
standard 81/* X 1 1-inch binder. The length of the sheet determined the diameter
of the recording drum. The recording drum was found to be more convenient
for audio measurements than a continuous feed, as it made it possible to calibrate
the graph in terms of frequency and to record upon the same sheet as many as six
different curves in differently colored inks so that comparisons could be made.

666

SYMPOSIUM ON TRANSMISSION METERS

After checking all the available recorders it was decided that we should elimi-
nate the meter and the magnetic clutch types of movement, and, finally, the only
type that remained for development was the controlled-motor type.

It was then found necessary only to choose an actuating switch and motor that
would operate within the limits set by our previously determined recording speed.

From the first, a dynamic relay has been used for controlling the drive motor.
Many attempts were made to discard this unit only to find that it presented the
most durable and readily adjustable switch that could be obtained. In earlier
experiments the recorder drive motor was of the universal type with two senes
fields, the direction of rotation being determined by the position in which the
dynamic relay operated.

Again we learned that the recording speed was determined by the braking^ and
coasting of the motor after cessation of excitation. The final choice settled down
to a two-phase induction motor with dynamic braking, which enabled uniform

M

7

FIG. 3. Same as Fig. 2, taken more slowly.

integration at any level. The two-phase motor is operated from the single-phase
line, the second phase being supplied by a condenser. The latter phase determines
the rotation of the motor and when both windings are connected to the same
phase dynamic braking takes place.

The pen arm also carries the attenuator arm which operates in the microphone
amplifier to balance the control system. The final choice for the drum drive
motor was a series type of motor with a field speed control. This was found to
be most convenient, and running a quick curve to determine the general trend of
the system, it was found that the accuracy of the trace could be improved by a
longer recording period. Fig. 2 is a curve of a 6-inch permanent-magnet dynamic
loud speaker run at high speed, while Fig. 3 is a curve on the same unit taken more
slowly. The completed recorder was then supplied with switches that would cut
the power supply when the curve was finished. After the recorder was com-
pleted it became obvious at once that a complete unit that would contain the
beat-frequency oscillator, the microphone amplifier, the audio rectifier, the
recorder control, and the recorder and associated power supplies would provide
a unit that would permit running practically any audio curve automatically.

DISCUSSION

The following is a discussion held jointly of five papers presented at the Con-
vention of the Society at Hollywood, Calif., on May 25, 1937, constituting a sym-
posium on transmission meters and including the following papers:

"A Transmission- Measuring System Utilizing a Graphic Recording Meter";
W. W. Lindsay, Jr.

"A New Instrument for Producing Automatically a Graphic Record of Audio-
Frequency Characteristics"; A. D. MacLeod

"A Continuous Level Recorder for Routine Studio and Theater Measurements";
G. M. Sprague and J. K. Hilliard

"A Curve-Plotting Transmission Meter"; L. A. Aicholtz

"A Curve-Plotting Transmission Meter"; L. D. Grignon

The first paper, that by W. W. Linsday, Jr., was published in the July issue of
the Journal; the four other papers appear in this issue immediately preceding this
discussion.

MR. SKINNER: Has anything been done about using photographic methods in
this work? I have done some work of that sort, but did not have an amplifier
that would produce a logarithmic scale. I have used a three-element oscillo-
graph, one element of which recorded the input; another element recorded the
frequencies shown on the dial ; and a third made the curve of the equipment, all
photographed simultaneously on a piece of bromide paper. A loud speaker could
be measured in seven seconds. The method was described in J. A . I. E. E. in 1929.
There was no possibility, however, of completing the run before the formation of
a standing wave.

MR. HAWKINS: Since many tests are routine, has anyone thought of using
for such tests the cathode-ray oscilloscope with a wide-range warble? The whole
spectrum would be covered in a twenty-fourth of a second, and a suitable sweep
circuit could fix tfie curve upon the screen of the oscilloscope. That would enable
a simple positive or negative report as to whether the circuit were satisfactory. If
satisfactory, you could go over the curves with a slow-speed machine, perhaps
a hand-operated set, of sufficient accuracy to find out where the trouble lay.

Another point relates to the matter of obtaining a logarithmic scale from a linear
function by using two dissimilar tubes in parallel, to produce either characteristic
required. I was able to get a fairly accurate logarithmic scale over a range of 40
db. by using two 6C6 pentodes in parallel, with different screen voltages, which, of
course, gave each of the tubes a different amplification factor.

MR. HILLIARD : Another method of making loud speaker acoustic measurements
is to impress the output from the loud speaker upon a light-valve. By rotating
the oscillator at a very fast rate the effect of standing waves is reduced. That
seems to be a very logical method, as it is not necessary to use a warble tone.

MR. TASKER: It should be noted, as mentioned by one of the speakers, that
when the oscillator is changing frequency rapidly, frequency modulations are
present and there is a tendency to get a false result.

667

668 SYMPOSIUM ON TRANSMISSION METERS

MR. SKINNER: In agreement with that statement, when we took only the
seven seconds to check the standing waves, the loud speaker runs were made under
a condition in which there were no standing waves. However, fast methods of
testing a speaker are of interest in finding out whether the speaker will respond.

MR. TASKER: It might be interesting to know the relative speeds of the
several instruments described. With the Deutschmann device something like 50
seconds were required—

MR. LINDSAY: Sixty seconds for a complete run.

MR. SPRAGUE : Thirty-five seconds.

MR. AICHOLTZ: Exactly 60 seconds.

MR. GRIGNON: Seventy-five seconds.

MR. TASKER: The figures vary considerably, but are somewhere around a
minute. What are the input levels to the recording meter amplifiers at full-scale
deflection?

MR. LINDSAY: Plus 10 db. for the full scale.

MR. MACLEOD: Minus 85 db. for the full scale of the instrument.

MR. SPRAGUE: Plus 10 db. for full-scale deflection without amplification, and
—92 db. with amplifiers included in the unit.

MR. AICHOLTZ: Minus 13 at full-scale deflection.

MR. GRIGNON: Under normal conditions, ±6 db. for the maximum level on
the linear portion of the scale.

MR. POWERS: I think it was said that it might be desirable to keep permanent
records of the test of overall peaks of each shot made. Have any of these instru-
ments been used for that purpose?

MR. LINDSAY : We made some records of that sort, and found them useful un-
der certain conditions. However, we do not generally make them.

MR. HAWKINS: I had occasion to be associated with the construction of ap-
paratus for recording the peaks and checking the mixing, and we electrically
counted the peaks of 90 per cent modulation with a peak relay. Another measured
the time during which the modulation was in excess of 35 per cent to give an
estimate of the time in which there were no signal peaks present.

NEW MOTION PICTURE APPARATUS

During the Conventions of the Society, symposiums on new motion picture appara-
tus are held, in which various manufacturers of equipment describe and demonstrate
their new products and developments. Some of this equipment is described in the
following pages; the remainder will be published in subsequent issues of the Journal.

A NEW TYPE OF DOUBLE-FILM ATTACHMENT*

E. C. MANDERFELD**

Since it is the customary practice in the motion picture industry to record sound
and picture on separate negatives and make separate piints for daily reproduc-
tion and cutting purposes, means must be provided for the projection of both
films in synchronism. This was done originally by operating a sound "dummy"
interlocked to the standard projector. More recently, however, the use of double-
film attachments on the projector has come into general use. The type of double-
film attachment described here has been designed as a complementary part of
the new high-quality reproducer recently introduced by Electrical Research Prod-
ucts, Inc.1

In this design considerable emphasis has been directed toward reducing space
requirements for the attachment and at the same time for facilitating operation.
To effect the maximum economy of space, the regular lower magazine is replaced
by a special magazine (Figs. 1, 2, and 3), which is part of the double-film attach-
ment, containing two take-up spindles and one feed spindle, all mounted in one
common housing. By reference to Fig. 2, it will be noted that one take-up spindle
is mounted in the normal position and is so centered that 2000-ft. reels can be ac-
commodated. The other two spindles, shown in Fig. 3, are so placed as to allow
only 1000-ft. reels to be used. The latter are the feed spindle for the sound-film
and the take-up spindle for the picture film, and are used only for double-film
projection.

Fig. 4 shows the paths of the two films into and out of the lower magazine. The
picture film as it leaves the intermittent of the Simplex head is fed to the left upper
side of the standard 16-tooth hold -back sprocket. From there the film passes
over a flanged idler roller mounted above and slightly to the right of this sprocket.
The film then passes under one and over another flanged idler roller in the guide-

* Presented at the Spring, 1937, Meeting at Hollywood, Calif.; received
June 21, 1937.

** Electrical Research Products, Inc., Hollywood, Calif.

669

670

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

roller housing mounted on the front of the Simplex head. From there the film
passes down through the film-chute to the take-up spindle in the double-film
magazine.

The sound-film is led up from the magazine through the film-chute to the guide-

FIG. 1. Rear of special magazine and v-belt drive.

roller housing, over idler rollers to the lower side of the 16-tooth Simplex sprocket.
From there the film passes directly down to the scanning drum of the sound-
head, over the two 16-tooth sprockets in the sound-head to the usual take-up
spindle mounted in the left side of the double-film magazine.

The two additional idler rollers referred to above are readily mounted above

Dec., 1937]

NEW MOTION PICTURE APPARATUS

671

672

NEW MOTION PICTURE APPARATUS [J. S. M. p. E.

the 16-tooth sprocket in the Simplex head. They are quickly installed by means
of ordinary hand tools and require no accurate alignment.

By reference to Figs. 2 and 3, the door hinging for the lower magazine may
be noted. This door is provided with a double hinge for opening only the left

FIG. 4. Paths of the two films into and out of the lower magazine.

half of the magazine (Fig. 2), when standard Movietone prints are being repro-
duced. When double-film reproduction is required (Fig. 3), the entire door can
be pulled open by exerting a slight extra pull on the door knob. To facilitate
threading, the film compartment door of the sound-head has been removed, and
the design shown in Fig. 3 has been adopted to serve as a combined door for the
sound-head, guide-roller housing, and lower portion of the Simplex head.

For use in running half-width film, sometimes known as split film, special roll-

Dec., 1937] NEW MOTION PICTURE APPARATUS 673

ers are provided in the magazine and guide-roller housing. These rollers are
quickly adjustable by hand for either half -width or standard film. In the sound-
head itself, two hardened guiding fingers are provided that can readily be swung
into position for half- width film. These fingers are shown swung back out of
position in Fig. 4.

The lower magazine design permits the Simplex head to have the same angle
of tilt relative to the pedestal as originally provided in the standard machine when
equipped with the standard lower magazine. The additional take-up spindle is
driven by the normal take-up spindle shaft by means of a K-belt (Fig. 1), thereby
eliminating noise. The entire double-film unit, except for the sheet-iron maga-
zine door, is constructed of cast aluminum. It is finished in baked black enamel.

Tests of this novel design in Hollywood studios have shown the double-film
attachment to be thoroughly reliable over an extended period of use under ordi-
nary conditions. The installation of the units on the projector is a simple opera-
tion. Maintenance, due to the simplicity of design, is reduced to a minimum,
while the ease of threading and operating makes the attachment very attractive
to the projectionist.

REFERENCE

1 DAVIDSON, J. C. : "A New High-Quality Film Reproducer," /. Soc. Mot.
Pict. Eng., XXVIII (Feb., 1937), No. 2, p. 202.

A COMBINED VIEWING AND PROJECTION MACHINE
WITH OR WITHOUT SOUND*

I. SERRURIER**

When editing motion pictures it is frequently desirable to view a larger image
of the scene than is possible through the magnifier of the conventional Moviola
film-viewing machines now generally used in the cutting rooms.

To see the picture on a small screen is much easier for the eyes of the film editor,
who works with pictures of this kind for many hours each day. It is of particular
benefit when synchronizing pictured lip movements with the corresponding sound-
track, and when "previewing" all or part of a picture with the director or others,
near the end of the film editor's work.

For several years the Moviola Company has manufactured special projectors
for this purpose, but the use of a projector makes it necessary to interrupt the
work in the cutting room and to move to a darkened projection room. Moreover,
the film in the projector is harder to get at, and runs vertically downward, with
the picture upside down in the aperture while the picture on the screen is right
side up.

* Presented at the Spring, 1937, Meeting at Hollywood, Calif. ; received May
28, 1937.

** The Moviola Company, Hollywood, Calif.

674

NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

To overcome these disadvantages common to all conventional projectors, a
modification of the Moviola design has been developed, called the "Preview
Moviola." It incorporates all the established Moviola features, and, in addition,
makes it possible to view a considerably enlarged image of the picture alongside
the film, with all details in the same relative positions as in the picture on the
film under the viewing lens.

The new design is wholly self-contained, and does not require that the room be
darkened. It is essentially an addition to the present Moviola design, and requires
no adjustment to change from normal Moviola operation to larger-image view-
ing. It is possible at any time, even when the film is running, to change from the
former to the latter or vice versa.

The basic feature of the new design is a cast aluminum shadow-box, which is
mounted below the regular Moviola picture head and extends along the same axis
as the regular viewing lens. The image is projected through the shadow-

FIG. 1. Optical arrangement of preview machine.

box to a spherical mirror at the bottom, which reflects it upward and slightly to
the right, to a focus on a ground-glass screen, 51/* by 6Vz inches in size, mounted
beside the regular viewing magnifier (Fig. 1).

The light for projecting comes from a 6-volt, 50-cp. or 100-cp. Mazda globe
mounted in a lamp house very similar to those that hold the exciter lamps for
Moviola sound pick-ups. The lamp house is mounted upon a hinge so that it may
be swung over the regular viewing magnifier when it is desired to project the
picture upon the larger screen (Fig. 2).

The magnifier serves as the condenser when projecting, and it was by practical
experiment rather than calculation and design that it was found that this regular
magnifier would serve very satisfactorily as a condenser, without any alteration
of its parts. Even the hinged mounting of the magnifier remains unchanged, so
that it can readily be lifted up to afford access to the film itself for making identi-
fying markings.

Below the film-carrying aperture is fitted a shutter of the barrel type, which can
be disconnected when it is not wanted to use the shutter, as in extreme slow-

Dec., 1937] NEW MOTION PICTURE APPARATUS 675

speed projection. The shutter can readily be disconnected or reconnected, and
it is impossible to reconnect it out of time with the film movement.

Beneath the shutter is mounted a standard Series / projection lens, which pro-
jects a virtual image a short distance in front of the spherical mirror at the bot-
tom of the shadow-box. This mirror, which is necessarily a first-surface mirror,
reflects the image upward and somewhat laterally to form a real image on the
ground-glass screen, which is, of course, well shaded from room light.

In addition to the standard Moviola mechanism for framing the image at the
viewing aperture, it was necessary to be able to frame the image reflected by the
mirror to the ground-glass screen, and to frame it both up and down and laterally.
This was achieved by mounting the mirror in a gimbal mount, free to move on two

Bffc:
FIG. 2. Large-image viewing in the Preview Moviola.

axes. A metal arm, rigidly attached to the mirror mount at its lower end, extends
upward inside the shadow-box. A guiding rod, parallel to the side of the film,
is provided for the arm, and vertical framing of the picture on the screen is ac-
complished by sliding the end of the arm along this rod. The guiding rod is
mounted eccentrically on pivots in the top and bottom of the shadow-box, and by
turning it slightly on the pivots it moves slightly sidewise, thus causing a lateral
motion of the picture on the screen. This adjustment makes it possible also
to put the image of the sound-track on the screen.

It seemed desirable to provide also adjustment so that the screen image could
be made to fit exactly the frame around the screen, or somewhat larger or smaller,
as desired by the operators. This was made possible by mounting the entire
reflector assembly, including the gimbal ring mounting and its controlling ram,
so that its location could be adjusted along the axis of the projecting lens. This

676 NEW MOTION PICTURE APPARATUS [J. S. M. P. E.

is quite a delicate adjustment, and a very slight variation in the location of the
spherical reflector makes a substantial difference in the size of the picture on the
screen. This construction also has the further advantage that slight variations
of the focal length of the projection lenses and reflectors to be used in machines of
this type may be easily taken care of.

The first-surface reflector is very well protected in the entirely enclosed shadow-
box, which does not have to be opened for adjustment after the machine is placed
in operation.

When using the Preview Moviola, the change from ordinary Moviola magnifier
viewing to projection on the ground-glass screen is effected by merely swinging the
projection lamp house upon its hinge into a position directly over the magnifier,
as has previously been stated. A pair of mercury switches in the base of the lamp

FIG. 3. The Preview Moviola, with the shadow-box.

house automatically turn off the viewing lamp and turn on the projection lamp.
At the same time an automatic mechanical linkage folds away the opal glass
diffusing panel below the viewing aperture and a white reflecting plate which re-
flects the light for magnifier viewing from the viewing lamp. This viewing lamp
is necessarily placed to one side in order to provide a free channel for projection.
Swinging the projection lamp house to one side reverses these automatic actions
and instantly renders the frame in the aperture visible through the magnifier
(Fig. 3).

All other features of the machine are identical with those of standard Moviolas,
and the picture-head described here can be combined with one or more standard
Moviola sound-heads for sound on composite film or for sound on separate film.
The motor drive can be either variable-speed, nearly constant speed, or synchro-
nous speed, and the direction of rotation is instantly reversible. An electric brake
can be applied for stopping on the frame that is under the lens. The machine

Dec., 1937]

NEW MOTION PICTURE APPARATUS

677

shown in Fig. 4 is fitted to reproduce sound from composite sound-track as well
as from a separate sound-track. Film may be fed into the machine either from
short rolls held in the hand or from reels mounted upon double-action feed and
take-up spindles.

FIG. 4. The complete unit.

The new model, in brief, combines all the features of previous Moviolas, and,
in addition, by means of the special self-contained projection feature, permits
the operator at any time to view an enlarged image of the scene without leaving
the cutting room or making any special adjustments of this machine.

CURRENT LITERATURE OF INTEREST TO THE MOTION PICTURE

ENGINEER

The editors present for convenient reference a list of articles dealing with subjects
cognate to motion picture engineering published in a number of selected journals.
Photostatic copies may be obtained from the Library of Congress, Washington, D. C.,
or from the New York Public Library, New York, N. Y. Micro copies of articles
in those magazines that are available may be obtained from the Library of the U. S.
Department of Agriculture, Washington, D. C.

American Cinematographer

18 (Sept., 1937), No. 9
Two New Films for Duplicating Work (p. 360).

Television Will Supplement but Won't Supplant (p. 366).
MGM to Make Wide Use of Tone-Tint Merging (p. 372).

Bell Laboratories Record

16 (Sept., 1937), No. 1
Magnetic Recording and Reproducing (p. 2).

Cine-Technician

3 (Aug.-Sept., 1937), No. 11
After the Revolution (p. 97).

Communications

(Merger of Radio Engineering and Communications and
Broadcast Engineering)

17 (Sept., 1937), No. 9
Disk Recording (p. 11).

Methods of Analyzing Acoustic-Feedback Howl (p. 28).

Educational Screen '

16 (Sept., 1937), No. 7
The Immediate Needs in Visual Education (p. 213).

Electronics

10 (Sept., 1937), No. 9
Television in Europe (p. 13).

Filmtechnik

13 (Aug. 21, 1937), No. 12

Querschnitt durch die Funkausstellung 1937 (Review of
the Radio Exposition of 1937) (p. 127).

678

C. E. IVES AND

J. I. CRABTREE
R. R. BEAL

J. M. NlCKOLAUS

C. N. HlCKMAN

T. L. DOWNEY
C. O. CAULTON

F. D. McCLUSKY

M. P. WILDER

P. HATSCHEK

CURRENT LITERATURE 679

Tonfilmaufnahme : Verbesserungen durch "Eurocord"
(Improvement in Sound Recording by the Use of the
"Eurocord") (p. 136).

Filmtechnik

13 (Sept. 11, 1937), No. 13

Kunstliche Polarisatoren (Synthetic Polarizers) (p. 145) E. NAHRING
Bildzerleger Linsenkranzabtaster (Optical System for Lens

Drum Picture Scanner) (p. 152). E. SCHRIEWER

International Photographer

9 (Sept., 1937), No. 8

Common Sense of Color (p. 7). D. K. ALLISON

Curtis One-Shot Three- Color Camera (p. 12) D. HOOPER

Lighting-Sets (p. 24). R. RENNEHAN

Negative- Positive Color (p. 27). D. HOOPER

International Projectionist

12 (Sept., 1937), No. 9
Typical Troubles in Modern Sound Reproducing Units — IV

(p. 7). L. CHADBOURNE

The Magnesium- Copper Sulphide Rectifier for Arc Supply

(p. 24). J. K. ELDERKIN

Journal of the Biological Photographic Association

6 (Sept., 1937), No. 1
The Fundamentals of Animated Scientific Drawing and

Cinematography (p. 1). C. D. CLARKE

Surgical Motion Pictures: Equipment and Technic (p. 25). L. A. JULIN

Kinotechnik

19 (Aug., 1937), No. 9
Technische Bewertung von Schmalfilmgeraten (Technical

Evaluation of Substandard Film Equipment) (p. 200). J. RIECK
Ein Beitrag zur Vervollkommnung des Oberflachen-
spiegels fur die Gebiete hochwertiger Optik (Contribu-
tion to the Improvement of Reflecting Surface in the
Field of High-Grade Optics) (p. 203). M. AUWARTER

Motion Picture Herald (Better Theaters Section)

128 (Sept. 18, 1937), No. 12
Theater Acoustics Today: 5 — Characteristics of Acoustic

Materials (p. 31). C. C. POTWIN

Photographische Industrie

35 (Aug. 25, 1937), No. 34

Filmbeferderung und Filmaufbewahrung bei kabinenlosen
Filmvorfuhrungen (Film Transport and Storage When
Projecting outside a Booth) (p. 913).

680 CURRENT LITERATURE

35 (Sept. 1, 1937), No. 35

Panoramafilm mit alten und neuen Mitteln (Old and New
Means of Panoraming) (p. 937).

Photographische Industrie

35 (Sept. 15, 1937), No. 7
Normungsprobleme beim Umkopieren (The Problem of

Standardization in Optical Printing) (p. 985). P. HATSCHEK

Proceedings of the Institute of Radio Engineers

25 (Sept., 1937), No. 9
Notes on Some Practical Comparison Tests Made Between

Several Acoustic Measurement Methods (p. 1136). E. T. DICKEY

Technique Cinematographique

9 (Aug., 1937), No. 80
Le Controle Visuel de la Puissance d'Enregistrement

(Visual Control of the Recording Current) (p. 983). R. HARDY
Les Projecteurs pur Jeux de Lumiere (Light Effects with
Projectors) (p. 985).

SOCIETY ANNOUNCEMENTS
SPRING, 1938, CONVENTION

Work of the Papers Committee in soliciting papers and presentations for the
Spring, 1938, Convention at Washington, D. C., to be held April 25th to 28th,
inclusive, has already begun. The Wardman Park Hotel, as in previous years,
will be the headquarters.

Details of the Convention will be published in succeeding issues of the JOURNAL,
and members are urged to make their plans early for attending.

Rates guaranteed to SMPE delegates attending the Convention are as follows:
One person, room and bath $ 3 . 50

Two persons, standard bed 5.00

Two persons, twin beds 5 . 00

Parlor suite, one person 9 . 00

Parlor suite, two persons 1 1 . 00

ATLANTIC COAST SECTION

At a meeting held on November 17th, at the Hotel Pennsylvania, New York,
N. Y., Dr. L. A. Jones, of the Kodak Research Laboratories, Rochester, N. Y.,
presented a paper on the subject of "Inter-Relationships of Various Aspects of
Color."

Despite the fact that this subject was not directly concerned with motion
pictures, but dealt rather with the nomenclature and psychophysical aspects of
color, the meeting was very well attended and the discussion following the pres-
entation indicated an intense interest in the subject on the part of the 150 persons
present.

Interesting meetings for the next two months have already been arranged, and
announcements will be mailed to the membership in the near future.

Nominations of Officers and Managers of the Section for 1938 are as follows:
Chairman: G. Friedl, Jr.
Secretary-Treasurer: D. E. Hyndman
Manager: P. J. Larsen

The remaining member of the Board of Managers of the Section is H. Griffin,
whose term has yet another year to run. The retiring Manager is M. C. Batsel.

MID-WEST SECTION

The regular monthly meeting of the Section was held on October 27th in the
meeting rooms of The Western Society of Engineers, in the Engineering Building,
Chicago. Mr. Carl G. Miller of the Weston Electrical Instrument Corporation,
Chicago, presented a demonstration of the latest developments in instruments
for measuring photographic exposure, and discussed the subject of "Importance
of Exposure in Photography."

681

682 SOCIETY ANNOUNCEMENTS [J. S. M. P. E.

Nominations of Officers and Managers of the Section for the year 1938 are as
follows :

Chairman: S. A. Lukes
Secretary-Treasurer: A. Shapiro
Manager: G. W. Baker

Officers and Managers whose terms expire December 31, 1937, are as follows:
Chairman, C. H. Stone; Secretary-Treasurer, S. A. Lukes; and Manager, O. B.
Depue. The remaining member of the Board of Managers is B. E. Stechbart,
whose term has yet another year to run.

PACIFIC COAST SECTION

On November 9, 1937, members of the Pacific Coast Section were the guests of
the Los Angeles Section of the American Institute of Electrical Engineers, at a
meeting held at Trinity Auditorium in Los Angeles. The arrangement was made
through the courtesy of the Southern Telephone Company. Dr. J. O. Perrine of
the American Telephone and Telegraph Company presented a talk on the subject
of "Waves, Words, and Wires," in which he described in a non-technical manner
some of the latest developments in the art of telephone transmission and sound
reproduction, illustrating the lecture with demonstration equipment. Among the
effects demonstrated were those of electrical echo, singing, overloading of ampli-
fiers, and noise, and how such detrimental features are eliminated or reduced. An
additional demonstration of high-fidelity reproduction of sound and music, with
a special multi-throated loud speaker was given.

Nominations of Officers and Managers of the Section for 1938 are as follows:

Chairman: J. O. Aalberg

Secretary- Treasurer: Q. A. Chambers

Manager: C. W. Handley

Officers and Managers whose terms expire December 31, 1937, are as follows:
Chairman, K. F. Morgan; Secretary- Treasurer, G. A. Chambers; Manager, J. O.
Aalberg. Mr. Morgan was elected Executive Vice-President of the Society in
the recent elections. The remaining member of the Board of Managers is H. W.
Moyse, whose term has another year to run.

ADMISSIONS COMMITTEE

At a recent meeting of the Admissions Committee, at the General Office of the
Society, the following applicants for membership were admitted to the Associate
grade:

ANDERSON, G. A. BARDFIELD, D.

24 Charles St., 769 Bryant Ave.,

Council Bluffs, Iowa. New York« N- Y-

BARNES, E. J.

BAKER, G. S. E. J. Barnes Associates,

Wootton Livesey Road, 101 W. 31st St.,

Ludlow, England. New York, N. Y.

Dec., 1937]

SOCIETY ANNOUNCEMENTS

683

BEALS, C. W.
41-41 41st St.,

Long Island City, N. Y.
BICKER, F. L.
4, Sarphatikade,

Amsterdam, Holland.
BOENIGER, F. J.
Bolivia 2993,

Buenos Aires, Argentina.
BOWMAN, L. H.

Columbia Broadcasting System,
5939 Sunset Blvd.,
Los Angeles, Calif.
BRADEN, J.
Pako Corp.,

1006 N. Lyndale Ave.,
Minneapolis, Minn.
BURKE, E., JR.
1103 High St.,

Alameda, Calif.
CARSON, E. A.

Sunbeam Electric Mfg. Co.,

Evansville, Ind.
CHERRY, H.

1926 N. Stanley St.,
Philadelphia, Pa.
CHIARINI, T.
Kasr-El-Nil St., N. 23,

Cairo, Egypt.
COOK, J. C. M.
State Theater,

Napier, N. Z.
COOPER, G. H.
239 S. Mansfield Ave.,

Los Angeles, Calif.
CURRIE, J. T.
94 Park Ave.,

Westmont, N. J.
DHARAMSEY, M. I.
Bombay Talkies, Ltd.,

Malad, Bombay, India.
DIRADOUR, K. S.

127, Ave. Reine Nazlie,

Cairo, Egypt.
DUMAINE, J. L. M.
47, Rue Michelet,
Algeria.

DYKEMAN, H. E.
350 W. 55th St.,

New York, N. Y.
EGLOFF, O. L.
233 Park Place,

Brooklyn, N. Y.
FORTSON, C. W.

Wil-kin Theater Supply Corp.,
154 Walton St.,
Atlanta, Ga.
FRAIM, I. N.

DeLuxe Laboratories, Inc.,
441 W. 55th St.,
New York, N. Y.
FRETLAND, J. D.

1015 SW Morrison St.,

Portland, Ore.
GAGE, G. J.

5518 Barton St.,

Hollywood, Calif.
GARAVITO, H.

Spanish Language Center,
152 W. 42d St.,
New York, N. Y.
GILBERT, R. M.

4014 Randolph Ave.,
Oakland, Calif.

G-OLDMARK, P. C.

Columbia Broadcasting System,
485 Madison Ave.,
New York, N. Y.
GOVIL, H. G.

Govil India Corp., Ltd.,

Calcutta, India.
GRUBER, A.
725 W. 184th St.,

New York, N. Y.
HANSEN, W. G.
7660 Clinton St.,

Los Angeles, Calif.
HENDERSON, C. K.
102 Convent Ave.,

New York, N. Y.
HEYER, E. B.

Heyer-Schultz, Inc.,
39 Orange Road,
Montclair. N. J.

684

SOCIETY ANNOUNCEMENTS

[J. S. M. P. E.

HOBART, M.

Technicolor Motion Picture Corp.,

15 Broad St., New York, N. Y.
Hu, W. C. K.

Eastman Kodak Co.,
14 Queen's Road,
C. Hongkong, China.
JACQUES, H.

23 Boulevard d'Augurson,

Neuily-sur-Seine, France.
JENNINGS, W. N.
P. O. Box 65,
Easton, Pa.
KAMP, L. S.

1307 Spruce St.,

Philadelphia, Pa.
KLINE, P. E.
Box 171,

Balboa, C. Z.
KOSSOWSKY, A.

1920 Juan de Garay,
Olivos F.C.C.A.
Buenos-Aires, Argentina.
KOWALSKI, R. J.
4707 Oak Terrace,

Merchantville, N. J.
LEIBY, A. C.

20 Exchange Place,
New York, N. Y.
LEVY, S. B.

Akeley Camera Co.,
175 Varick St.,
New York, N. Y.
MAIER, E.

106 W. 73d St.,

New York. N. Y.
MALTAGHATI, P. J.

International Projector Corp.,
90 Gold St.,
New York, N. Y.
MAY, W. A.
511 Jerome St.,

Owosso, Mich.
MEAGHER, J. R.

RCA Manufacturing Co., Inc.,

Camden, N. J.
MESCO, S. W.
1475 E. 57th St.,
Brooklyn. N. Y

MURPHY, A.

Columbia Broadcasting System,
485 Madison Ave.,
New York, N. Y.

NUMANS, J. J.

2 Koninginnegrcieht,

The Hague, Holland.
NUNN, W. S.

10 Elmfield Ave.,
Teddington, Middlesex,
England.
OKRENT, J.

220 Boscobel Place,
. Bronx, N. Y.
PAIN, D. H.

Little Hill, Claremont Lane,

Esher, Surrey, England.
PAREENJA, R. D.

Bombay Talkies, Ltd.,

Malad, Bombay, India.
PATENT, J. R.
2121 Harrison Ave.,
New York, N. Y.
PEARLMAN, J.

International Projector Corp.,
90 Gold St.,
New York, N. Y.
PIER, K. M.

711 Almar Ave.,

Pacific Palisades, Calif.
PIRNER, E. J.

198—40 32d Ave.,
Flushing, N. Y.
PROCTOR, R. R.

659 Wrightwood Ave.,

Chicago, 111.
REICHEL, I. L.
Praha-Barrandov,
Czechoslovakia .
REMY, E. R

Campichuelo 29F,

Buenos Aires, Argentina.
SCHEY, G.

73 Gersthofer Strasse,

Vienna, Austria.
SEOUDI, A.

Agyptische Mission,

Berlin. W. 50, Germany.

Dec., 1937] SOCIETY ANNOUNCEMENTS 685

SHAFRON, P. 485 Fifth Ave.,

1762 Park Place, New York, N. Y.

Brooklyn, N. Y SNYDER, W. R.

SHELLY, L. C. 15140 Raymer St.,

1216 Burrard St., Van Nuys, Calif.

Vancover, B. C. SOEHL, C. A.

SHERMAN, L. F., JR. 230 Lincoln Place,

Loucks & Norling Studios, Brooklyn, N. Y.

245 W. 55th St., STOCK, N. E.

New York, N. Y. 3414 Jordan St.,

SIMONDS, C. W. Bayside West (L. I.), N. Y.

Eastman Kodak Co., WELCH, C. D.

Rochester, N. . 75 Crafton Ave.,

SIPP, E. F., JR. Pittsburgh (5), Pa.

25 Gladys Ave., YANDELL, J. N.

Hempstead, L. I. Box 518,

SMALL, F. G. Gem Theater,

Carl Zeiss, Inc., Kannapolis, N. C.

In addition, the following applicants have been admitted by vote of the
Board of Governors to the Fellow and Active grades:

KAUFMAN, M. L. (F) NORTON, B. (M)

National Screen Service Corp., 423 — 64th St.,

630 Ninth Ave., Brooklyn, N. Y.

New York, N. Y. TOBIN, J. M. (M)

M-°-M

BALSLEY, J. R. (M)

18 Elmcroft Road, Culver Cltv- Cf f"

Stamford, Conn. WISEMAN, E. F. (M)

Motion Picture Distributors Assn.

LESLIE, F. D. (M) Cathcart House,

33 Champs Elyesee, lie Castlereach St.,

Paris, France. Sydney, Australia.

JOURNAL

OF THE SOCIETY OF

MOTION PICTURE ENGINEERS

AUTHOR AND CLASSIFIED
INDEXES

VOLUME XXIX
JULY-DECEMBER, 1937

AUTHOR INDEX, VOLUME XXIX

JULY TO DECEMBER, 1937

Author

AICHOLTZ, L. A.
ALBERSHEIM, W. J.

ALBIN, F. G.
BAKER, J. O.
(and HASBROUCK, H. J.
and BATSEL, C. N.)
BAKER, T. T.

BATSEL, C. N.

(and HASBROUCK, H. J.
and BAKER, J. O.)
(and CARTWRIGHT,
C. H.)

BEAL, R. R.
BEGUN, S. J.

BEST, G. M.

BROWN, B.
CARTWRIGHT, C. H.
(and BATSEL, C. N.)

CECCARINI, O. O.
CRABTREE, J. I.

(and IVES, C. E.)
DIMMICK, G. L.

Di TORO, M. J.
FERMAUD, L. C.

Issue Page
Dec. 655

Sept. 274

417
489

A Curve-Plotting Transmission Meter
A Device for Direct Reproduction from

Variable- Density Sound Negatives
Mathematical Relations between Grain,

Background Noise, and Characteristic

Curve of Sound-Film Emulsions Oct.

A Linear Decibel-Scale Volume Indicator Nov.
Improved Noise-Reduction System for

High-Fidelity Recording Sept. 310

Some Lighting Problems in Color Cine-
matography Nov. 471

Improved Noise-Reduction System for

High-Fidelity Recording Sept. 310

Effect of Uneven Slit Illumination upon
Distortion in Several Types of Variable-
Width Records Nov. 476
RCA Developments in Television Aug. 121
Magnetic Recording-Reproducing Ma-
chine for Objective Speech Study Aug. 216
An Automatic Sound-Track Editing Ma-
chine Sept. 281
Prescoring for Song Sequences Oct. 356
Effect of Uneven Slit Illumination upon
Distortion in Several Types of Variable-
Width Records Nov. 476
Color Stills Oct. 397
Two New Films for Duplicating Work Sept. 317

The RCA Recording System and Its
Adaptation to Various Types of Sound-
Track Sept. 258

Distortion in the Reproduction of Hill-
and-Dale Recording Nov. 493

Denham Studios of London Film Produc-
tions. Ltd. July 770

690

INDEX

[J. S. M. P. E.

Author
FORREST, J. L.

(and WING, F. M.)
FRANK, J., JR.
FRITTS, E. C.

(and SANDVIK, O.)
G AUDIO, G.

GERLACH, E.
GOETZ, A.

(and GOULD, W. O.)

GOULD, W. O.
(and GOETZ, A.)

GRAVES, F.
GRIGNON, L. D.
HANDLEY, C. W.

HARKRIDER, J.
HASBROUCK, H. J.

(and BAKER, J. O.,
and BATSEL, C. N.)
HILLIARD, J. K.

(and SPRAGUE, G. M.)
HOPPER, F. L.

HOUGH, G. W.

(and LEAHY, W.)
IVES, C. E.

(and CRABTREE, J. I.)
JACKMAN, F. W.

KNUDSEN, V. O.
KOENIG, W.

KOERNER, A. M.

(and TUTTLE, C.)
LEAHY, W.

(and HOUGH, G. W.)
LINDSAY, W. W., JR.

MACLEOD, A. D.

Issue Page
The New Agfacolor Process Sept. 248

The Super Simplex Pedestal July 94

A Sound Kodascope Nov. 539

A New Viewpoint on the Lighting of

Motion Pictures Aug. 157

A New Dynamic Light-Valve Oct. 388

The Objective Quantitative Determina-
tion of the Graininess of Photographic
Emulsions Nov. 510

The Objective Quantitative Determina-
tion of the Graininess of Photographic
Emulsions Nov. 510

Handling Lighting Equipment in Produc-
tion Oct. 360
Light- Weight Stage Pick-Up Equipment Aug. 191
A Curve-Plotting Transmission Meter Dec. 660
The Advanced Technic of Technicolor

Lighting Aug. 169

Set Design from Script to Stage Oct. 358

Improved Noise-Reduction System for

High-Fidelity Recording Sept. 310

A Continuous Level Recorder for Routine

Studio and Theater Measurements Dec. 645

Power-Level Indicators for Sound Re-
cording Aug. 184

Infrared Negative as Applied to Special-
Effects Photography Sept. 326

Two New Films for Duplicating Work Sept. 317

The Evolution of Special-Effects Cine-
matography from an Engineering
Viewpoint Sept. 293

Recent Progress in Acoustics Sept. 233

The Organization and Activities of the
Research Council of the Academy of
Motion Picture Arts and Sciences Nov. 484

Standardization of Photographic Densi-
tometry Dec. 622

Infrared Negative as Applied to Special-
Effects Photography Sept. 326

A Transmission-Measuring System Uti-
lizing a Graphic Recording Meter July 68

An Automatic Audio-Frequency Graphic
Recorder Dec. 663

Dec., 1937]

INDEX

691

Author

MANDERFELD, E. C.
NICKOLATJS, J. M.

PFANNENSTIEHL, H.

PIVAR, M.
PRESNELL, R.
PREVIN, C.

QUIGLEY, M.

REEVES, A.
RETTINGER, M.
RICHARDSON, E. C.

SANDVIK, O.

(and FRITTS, E. C.)
SCOVILLE, R. R.

SERRURIER, I.
SHAPIRO, A.

SPRAGUE, G. M.

(and MILLIARD, J. K.)
STROHM, W. T.

TASKER, H. G.

TUTTLE, C.

(and KOERNER, A. M.)
WETZEL, E.
WHEELWRIGHT, G. W.

WING, F. M.

(and FORREST, J. L.)

Issue Page

A New Type of Double-Film Attachment Dec. 669
Toning Positive Film by Machine Meth-
ods July 65
A High-Precision Sound-Film Recording

Machine Aug. 202
Film Editing Oct. 363
Preparing a Story for Production Oct. 350
Setting Music to Pictures Oct. 372
Propaganda, Education, and the Enter-
tainment Film Dec. 592
Laboratory Equipment for the Smaller

Laboratory Oct. 446

Notes on the Velocity Microphone Dec. 629

Interference Effects in Rooms Dec. 635
Recent Developments in Motion Picture

Set Lighting Aug. 178

A Sound Kodascope Nov. 539

A Laboratory Flutter-Measuring Instru-
ment Aug. 209
A Combined Viewing and Projection Ma-
chine with or without Sound Dec. 673
Present Aspects in the Development of

16-Mm. Sound Sept. 303

A Continuous Level Recorder for Routine

Studio and Theater Measurements Dec. 645

Special Engineering Problems in a Motion

Picture Studio Aug. 197

A Dubbing Rehearsal Channel Sept. 286

Standardization of Photographic Densi-

tometry Dec. 622

Assembling a Final Sound-Track Oct. 374

Possibilities of Stereoscopic Motion Pic-
tures Dec. 603
^he New Agfacolor Process Sept. 248

CLASSIFIED INDEX, VOLUME XXIX

JULY TO DECEMBER, 1937

Acoustics

Recent Progress in Acoustics, V. O. Knudsen, No. 3 (Sept.), p. 233.
Interference Effects in Rooms, M. Rettinger, No. 6 (Dec.), p. 635.

Addresses

Proceedings of the Semi-Annual Banquet at New York, N. Y., October 13,

1937, No. 6 (Dec.), p. 577.
Propaganda, Education, and the Entertainment Film, M. Quigley, No. 6

(Dec.), p. 592.

Apertures

Report of the Projection Practice Committee, No. 6 (Dec.), p. 614.

Apparatus

A Transmission-Measuring System Utilizing a Graphic Recording Meter,

W. W. Lindsay, Jr., No. 1 (July), p. 68.

The Super Simplex Pedestal, J. Frank, Jr., No. 1 (July), p. 94.
Power-Level Indicators for Sound Recording, F. L. Hoppef, No. 2 (Aug.),

p. 184.

Light-Weight Stage Pick-Up Equipment, L. D. Grignon, No. 2 (Aug.), p. 191.
A High-Precision Sound-Film Recording Machine, H. Pfannenstiehl, No. 2

(Aug.), p. 202.
A Laboratory Flutter-Measuring Instrument, R. R. Scoville, No. 2 (Aug.),

p. 209.
Magnetic Recording-Reproducing Machine for Objective Speech Study, S. J.

Begun, No. 2 (Aug.), p. 216.
A Device for Direct Reproduction from Variable-Density Sound Negatives,

W. J. Albersheim, No. 3 (Sept.), p. 274.
An Automatic Sound-Track Editing Machine, G. M. Best, No. 3 (Sept.),

p. 281.

A Dubbing Rehearsal Channel, H. G. Tasker, No. 3 (Sept.), p. 286.
Improved Noise-Reduction System for High-Fidelity Recording, H. J. Has-

brouck, J. O. Baker, and C. N. Batsel, No. 3 (Sept.), p. 310.
Two New Films for Duplicating Work, C. E. Ives and J. I. Crabtree, No. 3

(Sept.), p. 317.
Infrared Negative as Applied to Special-Effects Photography, G. W. Hough

and W. Leahy, No. 3 (Sept.), p. 326.

A New Dynamic Light- Valve, E. Gerlach, No. 4 (Oct.), p. 388.
Laboratory Equipment for the Smaller Laboratory, A. Reeves, No. 4 (Oct.),

p. 446.

A Linear Decibel-Scale Volume Indicator, F. G. Albin, No. 5 (Nov.), p. 489.
A Sound Kodascope, E. C. Fritts and O. Sandvik, No. 5 (Nov.), p. 539.
692

INDEX

693

A Continuous Level Recorder for Routine Studio and Theater Measurements,

G. M. Sprague and J. K. Hillard, No. 6 (Dec.), p. 645.

A Curve-Plotting Transmission Meter, L. A. Aicholtz, No. 6 (Dec.), p. 655.
A Curve-Plotting Transmission Meter, L. D. Grignon, No. 6 (Dec.), p. 660.
An Automatic Audio-Frequency Graphic Recorder, A. D. MacLeod, No. 6

(Dec.), p. 663.
A New Type of Double-Film Attachment, E. C. Manderfeld, No. 6 (Dec.),

p. 669.
A Combined Viewing and Projection Machine with or without Sound, I. Ser-

rurier, No. 6 (Dec.), p. 673.

Color

Report of the Color Committee, No. 1 (July), p. 54.

The Advanced Technic of Technicolor Lighting, C. W. Handley, No. 2 (Aug.),

p. 169.
The New Agfacolor Process, J. L. Forrest and F. M. Wing, No. 3 (Sept.),

p. 248.

Color Stills, O. O. Ceccarini, No. 4 (Oct.), p. 397.
Some Lighting Problems in Color Cinematography, T. T. Baker, No. 5 (Nov.),

p. 471.

Committee Reports

Color
No. 1 (July), p. 54.

Exchange Practice
No. 1 (July), p. 50.

Historical and Museum
No. 2 (Aug.), p. 151.

Journal Award

No. 6 (Dec.), p. 580.
Membership

No. 1 (July), p. 63.

No. 6 (Dec.), p. 643.
Non- Theatrical Equipment

No. 1 (July), p. 57.

Papers

No. 2 (Aug.), p. 154.
Progress

No. 1 (July), p. 3.

Progress Award

No. 6 (Dec.), p. 583.
Projection Practice
No. 1 (July), p. 39.

Perforations for color cinematography; color-
sensitivity of photocells.

Projects; uniformity of exchange practice;
rewinding and patching.

New accessions and facilities.

Award to D. B. Judd.

Status report.
Status report.

Activities of British Institute of Cinematog-
raphy; analysis of proposals for screen
intensity.

Semi- Annual Report.

Award to E. W. Kellogg.

Projects under consideration; screen bright-
ness; screen illumination test-pattern; pro-

694 INDEX [J. S. M. P. E.

jection room plans; projector motors and

take-ups; sound screens; theater survey;

mutilation of film; picture apertures.

No. 6 (Dec.), P- 614. Current projects; projection apertures.

Standards

No. 2 (Aug.), p. 149. New standards drawings; screen brightness;

standard densities; 16-mm. projection reels.
No. 4 (Oct.), p. 376. Perforation standards.

Committees of the Society
No. 3 (Sept.), p. 334.

Densitometry

(See Sensitometry.)

Disk Recording

(See Sound Recording, Disk.)

Dubbing

A Dubbing Rehearsal Channel, H. G. Tasker, No. 3 (Sept.), p. 286.
Assembling a Final Sound-Track, E. Wetzel, No. 4 (Oct.), p. 374.

Duplication of Motion Picture Film

Two New Films for Duplicating Work, C. E. Ives and J. I. Crabtree, No. 3
(Sept.), p. 317.

Editing

An Automatic Sound-Track Editing Machine, G. M. Best, No. 3 (Sept.), p. 281.
Film Editing, M. Pivar, No. 4 (Oct.), p. 363.

A Combined Viewing and Projection Machine with or without Sound, I. Ser-
rurier, No. 6 (Dec.), p. 673.

Emulsions

Two New Films for Duplicating Work, C. E. Ives and J. I. Crabtree, No. 3

(Sept.), p. 317.
Infrared Negative as Applied to Special-Effects Photography, G. W. Hough and

W. Leahy, No. 3 (Sept.), p. 326.
The Objective Quantitative Determination of the Graininess of Photographic

Emulsions, A. Goetz and W. O. Gould, No. 5 (Nov.), p. 510.

Exchange Practice

(See Committee Reports, Exchange Practice.)

Film, Photographic Characteristics

Mathematical Relations between Grain, Background Noise, and Characteristic

Curve of Sound-Film Emulsions, W. J. Albersheim, No. 4 (Oct.), p. 417.
The Objective Quantitative Determination of the Graininess of Photographic

Emulsions, A. Goetz and W. O. Gould, No. 5 (Nov.), p. 510.

General

Progress in the Motion Picture Industry — Report of the Progress Committee,
No. 1 (July), p. 3.

Dec., 1937] INDEX 695

Spring, 1937, Convention at Hollywood, Calif., No. 1 (July), p. 106.
Television from the Standpoint of the Motion Picture Producing Industry —

Report of the Scientific Committee of the Research Council of the Academy

of Motion Picture Arts and Sciences, No. 2 (Aug.), p. 144.
Special Engineering Problems in a Motion Picture Studio, W. T. Strohm, No.

2 (Aug.), p. 197.

Recent Progress in Acoustics, V. O. Knudsen, No. 3 (Sept.), p. 233.
Present Aspects in the Development of 16-Mm. Sound, A. Shapiro, No. 3

(Sept.), p. 303.

How Motion Pictures Are Made — A Symposium of the Spring, 1937, Conven-
tion, Held at the Universal Studios, No. 4 (Oct.), p. 349.
The Organization and Activities of the Research Council of the Academy of

Motion Picture Arts and Sciences, W. Koenig, No. 5 (Nov.), p. 484.
Highlights of the Fall, 1937, Convention at New York, N. Y., October llth to

14th, No. 5 (Nov.), p. 550.
Proceedings of the Semi-Annual Banquet at New York, N. Y., October 13,

1937, No. 6 (Dec.), p. 577.
Propaganda, Education, and the Entertainment Film, M. Quigley, No. 6

(Dec.), p. 592.

Television Demonstration at the Fall Convention, No. 6 (Dec.), p. 596.
Possibilities of Stereoscopic Motion Pictures, G. W. Wheelwright, No. 6 (Dec.),

p. 603.

Illumination, Studio and Photographic

A New Viewpoint on the Lighting of Motion Pictures, G. Gaudio, No. 2 (Aug.),

p. 157.
The Advanced Technic of Technicolor Lighting, C. W. Handley, No. 2 (Aug.),

p. 169.
Recent Developments in Motion Picture Set Lighting, E. C. Richardson, No. 2

(Aug.), p. 178.

Handling Lighting Equipment in Production, F. Graves, No. 4 (Oct.), p. 360.
Some Lighting Problems in Color Cinematography, T. T. Baker, No. 5 (Nov.),

p. 471.

Index

Author, July-December, 1937, No. 6 (Dec.), p. 689.
Classified, July-December, 1937, No. 6 (Dec.), p. 692.

Infrared Photography

Infrared Negative as Applied to Special-Effects Photography, G. W. Hough
and W. Leahy, No. 3 (Sept.), p. 326.

Instruments

A Transmission-Measuring System Utilizing a Graphic Recording Meter,

W. W. Lindsay, Jr., No. 1 (July), p. 68.
Power-Level Indicators for Sound Recording, F. L. Hopper, No. 2 (Aug.),

p. 184.
A Laboratory Flutter-Measuring Instrument, R. R. Scoville, No. 2 (Aug.),

p. 219.
A Linear Decibel-Scale Volume Indicator, F. G. Albin, No. 5 (Nov.), p. 489.

696 INDEX [j. s. M. p. E.

A Continuous Level Recorder for Routine Studio and Theater Measurements.

G. M. Sprague and J. K. Milliard, No. 6 (Dec.), P- 645.
A Curve-Plotting Transmission Meter, L. A. Aicholtz, No. 6 (Dec.), p. 655.
A Curve-Plotting Transmission Meter, L. D. Grignon, No. 6 (Dec.), p. 660.
An Automatic Audio-Frequency Graphic Recorder, A. D. MacLeod, No. 6

(Dec.), p. 663.

Journal Award

Proceedings of the Semi-Annual Banquet at New York, N. Y., October 13,
1937, No. 6 (Dec.), p. 577.

Laboratory Apparatus

Laboratory Equipment for the Smaller Laboratory, A. Reeves, No. 4 (Oct.).
p. 446.

Lighting

(See Illumination, Studio and Photographic.)

Light-Valves

A New Dynamic Light- Valve, E. Gerlach, No. 4 (Oct.), p. 388.

Literature on Motion Picture Engineering

In each issue of the JOURNAL near the back of the issue.

Membership

Report of the Membership Committee, No. 1 (July), p. 63.
Lists of new members admitted published in each issue of the JOURNAL under
"Society Announcements."

Meters

(See Instruments.)

Microphones

Notes on the Velocity Microphone, M. Rettinger, No. 6 (Dec.), p. 629.

Miscellaneous

(See General.)

Museum

(See Committee Reports, Historical and Museum.)

Music for Motion Pictures

Setting Music to Pictures, C. Previn, No. 4 (Oct.), p. 372.

Non-Theatrical Equipment

(See Committee Reports, Non- Theatrical Equipment; and Sixteen- Millimeter
Equipment.)

Obituaries

Harry Pfannenstiehl, No. 1 (July), p. 104.
Frederick Eugene Ives, No. 2 (Aug.), p. 219.

Officers and Governors of the Society

On the reverse of the Contents page of each issue.
Nominations for 1938, No. 3 (Sept.), p. 343.

Dec., 1937] INDEX 697

Papers

(See Committee Reports, Papers.)

Perforations

Report of the Color Committee, No. 1 (July), p. 54.

Report of the Sub-Committee on Perforation Standards, No. 4 (Oct.), p. 376.

Prescoring

Prescoring for Song Sequences, B. Brown, No. 4 (Oct.), p. 356.

Processing

Laboratory Equipment for the Smaller Laboratory, A. Reeves, No. 4 (Oct.),
p. 446.

Processing Release Prints

Toning Positive Film by Machine Methods, J. M. Nickolaus, No. 1 (July),
p. 65.

Production

Denham Studios of London Film Productions, Ltd., L. D. Fermaud, No. 1
(July), p. 77.

How Motion Pictures Are Made — A Symposium of the Spring, 1937, Con-
vention, Held at the Universal Studios, No. 4 (Oct.), p. 349.

Progress

(See Committee Reports, Progress.)

Progress Award

Proceedings of the Semi-Annual Banquet at New York, N. Y., October 13,
1937, No. 6 (Dec.), p. 577.

Projection Practice

(See Committee Reports, Projection Practice.)

Projectors

The Super Simplex Pedestal, J. Frank, Jr., No. 1 (July), p. 94.

Sensitometry

Standardization of Photographic Densitometry, C. Tuttle and A. M. Koerner,
No. 6 (Dec.), p. 662.

Sets, Motion Picture

Set Design from Script to Stage, J. Harkrider, No. 4 (Oct.), p. 358.

Sixteen-Millimeter Equipment

(See also Committee Reports, N on- Theatrical Equipment.)

Present Aspects in the Development of 16-Mm. Sound, A. Shapiro, No. 3

(Sept.), p. 303.
A Sound Kodascope, E. C. Fritts and O. Sandvik, No. 5 (Nov.), p. 539.

Sound Recording,

Power-Level Indicators for Sound Recording, F. L. Hopper, No. 2 (Aug.),
p. 184.

698 INDEX [J. S. M. p. E.

Light-Weight Stage Pick-Up Equipment, L. D. Grignon, No. 2 (Aug.), p. 191.
Special Engineering Problems in a Motion Picture Studio, W. T. Strohm,

No. 2 (Aug.), p. 197.
Magnetic Recording-Reproducing Machine for Objective Speech Study, S. J.

Begun, No. 2 (Aug.), p. 216.

The RCA Recording System and Its Adaptation to Various Types of Sound-
Track, G. L. Dimmick, No. 3 (Sept.), p. 258.
Prescoring for Song Sequences, B. Brown, No. 4 (Oct.), p. 356.
Mathematical Relations between Grain, Background Noise, and Characteristic

Curve of Sound-Film Emulsions, W. J. Albersheim, No. 4 (Oct.), p. 417.
Assembling a Final Sound-Track, E. Wetzel, No. 4 (Oct.). p. 374.
A High-Precision Sound-Film Recording Machine, H. Pfannenstiehl, No. 2

(Aug.), p. 202.
Improved Noise-Reduction System for High-Fidelity Recording, H. J. Has-

brouck, J. O. Baker, and C. N. Batsel, No. 3 (Sept.), p. 310.
Effect of Uneven Slit Illumination upon Distortion in Several Types of

Variable-Width Records, C. N. Batsel and C. H. Cartwright, No. 5 (Nov.),

p. 476.
A New Type of Double-Film Attachment, E. C. Manderfeld, No. 6 (Dec.),

p. 669.

Sound Reproduction

A Device for Direct Reproduction from Variable- Density Sound Negatives,

W. J. Albersheim, No. 3 (Sept.), p. 274.
Distortion hi the Reproduction of Hill-and-Dale Recording, M. J. Di Toro,

No. 5 (Nov.), p. 493.
Magnetic Recording-Reproducing Machine for Objective Speech Study, S. J.

Begun, No. 2 (Aug.), p. 216.

Special-Effects Photography

The Evolution of Special-Effects Cinematography from an Engineering View-
point, F. W. Jackman, No. 3 (Sept.), p. 293.

Infrared Negative as Applied to Special-Effects Photography, G. W. Hough
and W. Leahy, No. 3 (Sept.), p. 326.

Standardization

Report of the Projection Practice Committee, No. 6 (Dec.), p. 614.
Standardization of Photographic Densitometry, C. Tuttle and A. M. Koerner,
No. 6 (Dec.), P- 622.

Standards

(See Committee Reports, Standards.)

Stereoscopy

Possibilities of Stereoscopic Motion Pictures, G. W. Wheelwright, No. 6 (Dec.),
p. 603.

Stories for Motion Pictures

Preparing a Story for Production, R. Presnell, No. 4 (Oct.), p. 350.

Dec., 1937] INDEX 699

Studio Equipment and Design

Denham Studios of London Film Productions, Ltd., L. C. Fermaud, No. 1

(July), p. 77.
The Advanced Technic of Technicolor Lighting, C. W. Handley, No. 2 (Aug.),

p. 169.
Recent Developments in Motion Picture Set Lighting, E. C. Richardson,

No. 2 (Aug.), p. 178.
Light-Weight Stage Pick-Up Equipment, L. D. Grignon, No. 2 (Aug.), p. 191.

Studio Lighting

(See Illumination, Studio and Photographic.)

Television

RCA Developments in Television, R. R. Beal, No. 2 (Aug.), p. 121.

Television from the Standpoint of the Motion Picture Producing Industry —
Report of the Scientific Committee of the Research Council of the Academy
of Motion Picture Arts and Sciences, No. 2 (Aug.), p. 144.

Television Demonstration at the Fall Convention, No. 6 (Dec.), p. 596.

Test-Films

SMPE Test-Films, No. 2 (Aug.), p. 227.

Toning

Toning Positive Film by Machine Methods, J. M. Nickolaus, No. 1 (July),
p. 65.

Transmission

A Transmission-Measuring System Utilizing a Graphic Recording Meter,

W. W. Lindsay, Jr., No. 1 (July), p. 68.
A Continuous Level Recorder for Routine Studio and Theater Measurements,

G. M. Sprague and J. K. Hilliard, No. 6 (Dec.), p. 645.
A Curve-Plotting Transmission Meter, L. A. Aicholtz, No. 6 (Dec.), p. 655.
A Curve-Plotting Transmission Meter, L. D. Grignon, No. 6 (Dec.), p. 660.
An Automatic Audio-Frequency Graphic Recorder, A. D. MacLeod, No. 6

(Dec.), p. 663.

Trick Photography

(See Special- Effects Photography.)

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